i'm just getting started (transititioning to) SQL Server, unfortunately the company has developers that have been doing all the table scripting, etc. on a cursory glance i found several tables that have column names that are also SQL reserved words. in DB2 for IBM i, i could just query the system catalogs for reserved words & am wondering if anyone has a script(or stored procedure) that will do that for SQL Server (currently on version 2012) my goal is to clean this up and have the tables rebuilt with proper column names and a script would be orders of magnitude faster than looking at each table's column listing.
Stripped and modified from a validation routine
For SQL Server's Reserved Words
Declare #Reserved table (Word varchar(100))
Insert Into #Reserved values
('ADD'),('ALL'),('ALTER'),('AND'),('ANY'),('AS'),('ASC'),('AUTHORIZATION'),('BACKUP'),('BEGIN'),('BETWEEN'),('BREAK'),('BROWSE'),('BULK'),('BY'),
('CASCADE'),('CASE'),('CHECK'),('CHECKPOINT'),('CLOSE'),('CLUSTERED'),('COALESCE'),('COLLATE'),('COLUMN'),('COMMIT'),('COMPUTE'),('CONSTRAINT'),
('CONTAINS'),('CONTAINSTABLE'),('CONTINUE'),('CONVERT'),('CREATE'),('CROSS'),('CURRENT'),('CURRENT_DATE'),('CURRENT_TIME'),('CURRENT_TIMESTAMP'),
('CURRENT_USER'),('CURSOR'),('DATABASE'),('DBCC'),('DEALLOCATE'),('DECLARE'),('DEFAULT'),('DELETE'),('DENY'),('DESC'),('DISK'),('DISTINCT'),
('DISTRIBUTED'),('DOUBLE'),('DROP'),('DUMP'),('ELSE'),('END'),('ERRLVL'),('ESCAPE'),('EXCEPT'),('EXEC'),('EXECUTE'),('EXISTS'),('EXIT'),('EXTERNAL'),
('FETCH'),('FILE'),('FILLFACTOR'),('FOR'),('FOREIGN'),('FREETEXT'),('FREETEXTTABLE'),('FROM'),('FULL'),('FUNCTION'),('GOTO'),('GRANT'),('GROUP'),
('HAVING'),('HOLDLOCK'),('IDENTITY'),('IDENTITY_INSERT'),('IDENTITYCOL'),('IF'),('IN'),('INDEX'),('INNER'),('INSERT'),('INTERSECT'),('INTO'),('IS'),
('JOIN'),('KEY'),('KILL'),('LEFT'),('LIKE'),('LINENO'),('LOAD'),('MERGE'),('NATIONAL'),('NOCHECK'),('NONCLUSTERED'),('NOT'),('NULL'),('NULLIF'),
('OF'),('OFF'),('OFFSETS'),('ON'),('OPEN'),('OPENDATASOURCE'),('OPENQUERY'),('OPENROWSET'),('OPENXML'),('OPTION'),('OR'),('ORDER'),('OUTER'),('OVER'),
('PERCENT'),('PIVOT'),('PLAN'),('PRECISION'),('PRIMARY'),('PRINT'),('PROC'),('PROCEDURE'),('PUBLIC'),('RAISERROR'),('READ'),('READTEXT'),('RECONFIGURE'),
('REFERENCES'),('REPLICATION'),('RESTORE'),('RESTRICT'),('RETURN'),('REVERT'),('REVOKE'),('RIGHT'),('ROLLBACK'),('ROWCOUNT'),('ROWGUIDCOL'),('RULE'),
('SAVE'),('SCHEMA'),('SECURITYAUDIT'),('SELECT'),('SEMANTICKEYPHRASETABLE'),('SEMANTICSIMILARITYDETAILSTABLE'),('SEMANTICSIMILARITYTABLE'),('SESSION_USER'),
('SET'),('SETUSER'),('SHUTDOWN'),('SOME'),('STATISTICS'),('SYSTEM_USER'),('TABLE'),('TABLESAMPLE'),('TEXTSIZE'),('THEN'),('TO'),('TOP'),('TRAN'),('TRANSACTION'),
('TRIGGER'),('TRUNCATE'),('TRY_CONVERT'),('TSEQUAL'),('UNION'),('UNIQUE'),('UNPIVOT'),('UPDATE'),('UPDATETEXT'),('USE'),('USER'),('VALUES'),('VARYING'),
('VIEW'),('WAITFOR'),('WHEN'),('WHERE'),('WHILE'),('WITH'),('WITHIN GROUP'),('WRITETEXT')
Select A.*
From INFORMATION_SCHEMA.COLUMNS A
Join #Reserved
on Column_Name = Word
Here is the list of reserved words https://msdn.microsoft.com/en-us/library/ms189822.aspx
You could copy these into a text editor or something then clean it up a little. Then throw them into a table then use that table as a reference.
Related
I have a Linked Server to the AS400 here. I'm trying to pull data from a field, but it is pulling over a million records when I only need about 20k.
I have a list of IDs that I need, and I'm trying to figure out how to pass that list into the OpenQuery.
Here is my OpenQuery:
SELECT * FROM OPENQUERY(AS400, '
SELECT
IMITNO, IMITD1, IMITD2, IMMFNO, IMBMTP, IMDSCO
FROM AS400.APLUS2FLE.ITMST
WHERE IMDSCO != ''Y''
')
I want to add WHERE IMITNO IN (SELECT item_id FROM as400_item_scope) but the as400_item_scope table is on the SQL machine, not the AS400. I looked at several examples and I can pass in a single variable, but I don't understand how to pass in a list/query like this.
I'm using latest SSMS, but SQL Server Version is 2008
You can't as far as I know...
Two options..
Insert the results of SELECT item_id FROM as400_item_scope into a (temporary?) table on the IBM i and then reference that table in your openquery.
build a comma delimited string with from the results of SELECT item_id FROM as400_item_scope and include that in your openquery string.
Depending on how many records are returned, you might run into issues with statement size trying to use option #2. Db2 for IBM i supports SQL statement of up to 2,097,152 bytes...
I'm trying to compare the schemas of two tables that exist in different databases. So far, I have this query
SELECT * FROM sys.columns WHERE object_id = OBJECT_ID('table1')
The only thing is that I don't know how to use the sys.columns to reference a database other than the one that the query is connected to. I tried this
SELECT * FROM db.sys.columns WHERE object_id = OBJECT_ID('table1')
but it didn't find anything.
I'm using SQL Server 2005
Any suggestions? thanks!
Take a look at redgate's SQL Compare.
To answer your specific question, you need to fully qualify the table reference.
SELECT * FROM db.sys.columns WHERE object_id = OBJECT_ID('db.SchemaName.table1')
Late one but hopefully useful.
Even though chama asked for SQL solutions I’d still recommend using a third party tools such as ApexSQL Diff or tools from Red Gate Joe already mentioned (I’ve used both and they worked great).
Reason is that query for comparing two tables using information schema has to be quite complex in order to catch all differences.
Note that all of the examples mentioned here only cover columns but none of the queries shown here will show the difference between nvarchar(20) and nvarchar(50) or difference in foreign keys or indexes or….
Short answer is yes – this is possible using information schema views but it can be rather complex if you want to compare every detail in those two tables.
all you need is to specify the DB name and shcema when calling OBJECT_ID function, like:
SELECT *
FROM DB_NAME.sys.columns
WHERE object_id = OBJECT_ID('DB_NAME.SHCEMA_NAME.table1')
Try the information_schema. eg:
select *
from
db1.information_schema.columns col1
join db2.information_schema.columns col2
on col1.table_catalog = col2.table_catalog
and col1.table_schema = col2.table_schema
and col1.column_name = col2.column_name
...
The information_schema simplifies sticking together the information from all the sys.columns,sys.objects etc. It exists automatically in your DB. I think its actually an ISO standard thing, so should work on various DB systems.
More information about the information_schema can be found here
Comparing whether the object or columns exists in both schemas is only a tiny bit of the solution. What if they exist in both databases but are different?
For my bsn ModuleStore project, I implemented a scripting routine which actually scripts most DB objects including table and view columns, indexes, namespaces etc. as XML using T-SQL code only. This may be a good place to start. You can find it on Google code, and the file in question (which generates the SQL query for dumping the object schema to XML) is here.
Code -
drop table #a
drop table #b
select *
into #a
from [databasename1].information_schema.columns a
--where table_name = 'aaa'
select *
into #b
from [databasename2].information_schema.columns b -- add linked server name and db as needed
--where table_name = 'bbb'
select distinct( a.table_name), b.TABLE_SCHEMA+ '.' + (b.table_name) TableName,b.TABLE_CATALOG DatabaseName
from #a a
right join #b b
on a.TABLE_NAME = b.TABLE_NAME and a.TABLE_SCHEMA = b.TABLE_SCHEMA
where a.table_name is null-- and a.table_name not like '%sync%'
Just in case you are using MS VS 2015 (Community is a free download). The SOL Server tools includes a Schema Comparison tool. "SQL Server Data Tools (SSDT) includes a Schema Compare utility that you can use to compare two database definitions".
This is a GPL Java program I wrote for comparing data in any two tables, with a common key and common columns, across any two heterogeneous databases using JDBC: https://sourceforge.net/projects/metaqa/
It intelligently forgives (numeric, string and date) data type differences by reducing them to a common format. The output is a sparse tab delimited file with .xls extension for use in a spreadsheet.
The program ingests SQL that is used to produce a source table that can be compared with the target table. The target table SQL can be generated automatically. The target table is read one row at a time and therefore should be indexed on the common key.
It detects missing rows on either side and common keyed rows with other optional column differences. Obviously the meta data can be accessed by SQL so whether your concern is with the data, or with the meta-data, it will still work.
This is very powerful in a data migration or System migration project, and also for auditing interfaces. You will be astounded at the number of errors it detects. Minimal false positives still do occur.
Informix, Oracle and SQL-Server were the first JDBC targets and you can extend that list if desired.
I have one problem in which i simply want to know how i can create a table that can easily Used as a back end for my solution that is in Vb 2010.
I also want to know that when we choose a data source in a vb.net that is for sql server Which we want to choose....simply which can be used Because there is 2 or 3 with little different name.....
I'm struggling to understand your question, but in an effort to help:
I'm guessing that you want to programmatically create a table to be used by other parts of your VB application, but that you need to ensure the table name is unique...? If I'm right in that assumption, then see below.
You can use this query:
SELECT *
FROM INFORMATION_SCHEMA.TABLES
WHERE table_type = 'BASE TABLE'
To get a list of table names currently in your database. You can compare the TABLE_NAME column values with your desired table name. If it exists already, change the name by adding an differentiator, eg: MyTable, MyTable1, MyTable2 etc.
Alternatively, SQL Server accepts Guids as table names.
Disclaimer: IMHO, If your table is not going to be temporary deciding table names in this manner is a pretty ugly solution and lacks supportability.
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I'm surprised this hasn't been posted yet. Any interesting tricks that you know about in Postgres? Obscure config options and scaling/perf tricks are particularly welcome.
I'm sure we can beat the 9 comments on the corresponding MySQL thread :)
Since postgres is a lot more sane than MySQL, there are not that many "tricks" to report on ;-)
The manual has some nice performance tips.
A few other performance related things to keep in mind:
Make sure autovacuum is turned on
Make sure you've gone through your postgres.conf (effective cache size, shared buffers, work mem ... lots of options there to tune).
Use pgpool or pgbouncer to keep your "real" database connections to a minimum
Learn how EXPLAIN and EXPLAIN ANALYZE works. Learn to read the output.
CLUSTER sorts data on disk according to an index. Can dramatically improve performance of large (mostly) read-only tables. Clustering is a one-time operation: when the table is subsequently updated, the changes are not clustered.
Here's a few things I've found useful that aren't config or performance related per se.
To see what's currently happening:
select * from pg_stat_activity;
Search misc functions:
select * from pg_proc WHERE proname ~* '^pg_.*'
Find size of database:
select pg_database_size('postgres');
select pg_size_pretty(pg_database_size('postgres'));
Find size of all databases:
select datname, pg_size_pretty(pg_database_size(datname)) as size
from pg_database;
Find size of tables and indexes:
select pg_size_pretty(pg_relation_size('public.customer'));
Or, to list all tables and indexes (probably easier to make a view of this):
select schemaname, relname,
pg_size_pretty(pg_relation_size(schemaname || '.' || relname)) as size
from (select schemaname, relname, 'table' as type
from pg_stat_user_tables
union all
select schemaname, relname, 'index' as type
from pg_stat_user_indexes) x;
Oh, and you can nest transactions, rollback partial transactions++
test=# begin;
BEGIN
test=# select count(*) from customer where name='test';
count
-------
0
(1 row)
test=# insert into customer (name) values ('test');
INSERT 0 1
test=# savepoint foo;
SAVEPOINT
test=# update customer set name='john';
UPDATE 3
test=# rollback to savepoint foo;
ROLLBACK
test=# commit;
COMMIT
test=# select count(*) from customer where name='test';
count
-------
1
(1 row)
The easiest trick to let postgresql perform a lot better (apart from setting and using proper indexes of course) is just to give it more RAM to work with (if you have not done so already). On most default installations the value for shared_buffers is way too low (in my opinion). You can set
shared_buffers
in postgresql.conf. Divide this number by 128 to get an approximation of the amount of memory (in MB) postgres can claim. If you up it enough this will make postgresql fly. Don't forget to restart postgresql.
On Linux systems, when postgresql won't start again you will probably have hit the kernel.shmmax limit. Set it higher with
sysctl -w kernel.shmmax=xxxx
To make this persist between boots, add a kernel.shmmax entry to /etc/sysctl.conf.
A whole bunch of Postgresql tricks can be found here:
http://www.postgres.cz/index.php/PostgreSQL_SQL_Tricks
Postgres has a very powerful datetime handling facility thanks to its INTERVAL support.
For example:
select NOW(), NOW() + '1 hour';
now | ?column?
-------------------------------+-------------------------------
2009-04-18 01:37:49.116614+00 | 2009-04-18 02:37:49.116614+00
(1 row)
select current_date ,(current_date + interval '1 year')::date;
date | date
---------------------+----------------
2014-10-17 | 2015-10-17
(1 row)
You can cast many strings to an INTERVAL type.
COPY
I'll start. Whenever I switch to Postgres from SQLite, I usually have some really big datasets. The key is to load your tables with COPY FROM rather than doing INSERTS. See documentation:
http://www.postgresql.org/docs/8.1/static/sql-copy.html
The following example copies a table to the client using the vertical bar (|) as the field delimiter:
COPY country TO STDOUT WITH DELIMITER '|';
To copy data from a file into the country table:
COPY country FROM '/usr1/proj/bray/sql/country_data';
See also here:
Faster bulk inserts in sqlite3?
My by far favorite is generate_series: at last a clean way to generate dummy rowsets.
Ability to use a correlated value in a LIMIT clause of a subquery:
SELECT (
SELECT exp_word
FROM mytable
OFFSET id
LIMIT 1
)
FROM othertable
Abitlity to use multiple parameters in custom aggregates (not covered by the documentation): see the article in my blog for an example.
One of the things I really like about Postgres is some of the data types supported in columns. For example, there are column types made for storing Network Addresses and Arrays. The corresponding functions (Network Addresses / Arrays) for these column types let you do a lot of complex operations inside queries that you'd have to do by processing results through code in MySQL or other database engines.
Arrays are really cool once you get to know 'em.
Lets say you would like to store some hyper links between pages. You might start by thinking about creating a Table kinda like this:
CREATE TABLE hyper.links (
tail INT4,
head INT4
);
If you needed to index the tail column, and you had, say 200,000,000 links-rows (like wikipedia would give you), you would find yourself with a huge Table and a huge Index.
However, with PostgreSQL, you could use this Table format instead:
CREATE TABLE hyper.links (
tail INT4,
head INT4[],
PRIMARY KEY(tail)
);
To get all heads for a link you could send a command like this (unnest() is standard since 8.4):
SELECT unnest(head) FROM hyper.links WHERE tail = $1;
This query is surprisingly fast when it is compared with the first option (unnest() is fast and the Index is way way smaller). Furthermore, your Table and Index will take up much less RAM-memory and HD-space, especially when your Arrays are so long that they are compressed to a Toast Table. Arrays are really powerful.
Note: while unnest() will generate rows out of an Array, array_agg() will aggregate rows into an Array.
Materialized Views are pretty easy to setup:
CREATE VIEW my_view AS SELECT id, AVG(my_col) FROM my_table GROUP BY id;
CREATE TABLE my_matview AS SELECT * FROM my_view;
That creates a new table, my_matview, with the columns and values of my_view. Triggers or a cron script can then be setup to keep the data up to date, or if you're lazy:
TRUNCATE my_matview;
INSERT INTO my_matview SELECT * FROM my_view;
Inheritance..infact Multiple Inheritance (as in parent-child "inheritance" not 1-to-1 relation inheritance which many web frameworks implement when working with postgres).
PostGIS (spatial extension), a wonderful add-on that offers comprehensive set of geometry functions and coordinates storage out of the box. Widely used in many open-source geo libs (e.g. OpenLayers,MapServer,Mapnik etc) and definitely way better than MySQL's spatial extensions.
Writing procedures in different languages e.g. C, Python,Perl etc (makes your life easir to code if you're a developer and not a db-admin).
Also all procedures can be stored externally (as modules) and can be called or imported at runtime by specified arguments. That way you can source control the code and debug the code easily.
A huge and comprehensive catalogue on all objects implemented in your database (i.e. tables,constraints,indexes,etc).
I always find it immensely helpful to run few queries and get all meta info e.g. ,constraint names and fields on which they have been implemented on, index names etc.
For me it all becomes extremely handy when I have to load new data or do massive updates in big tables (I would automatically disable triggers and drop indexes) and then recreate them again easily after processing has finished. Someone did an excellent job of writing handful of these queries.
http://www.alberton.info/postgresql_meta_info.html
Multiple schemas under one database, you can use it if your database has large number of tables, you can think of schemas as categories. All tables (regardless of it's schema) have access to all other tables and functions present in parent db.
You don't need to learn how to decipher "explain analyze" output, there is a tool: http://explain.depesz.com
select pg_size_pretty(200 * 1024)
pgcrypto: more cryptographic functions than many programming languages' crypto modules provide, all accessible direct from the database. It makes cryptographic stuff incredibly easy to Just Get Right.
A database can be copied with:
createdb -T old_db new_db
The documentation says:
this is not (yet) intended as a general-purpose "COPY DATABASE" facility
but it works well for me and is much faster than
createdb new_db
pg_dump old_db | psql new_db
Memory storage for throw-away data/global variables
You can create a tablespace that lives in the RAM, and tables (possibly unlogged, in 9.1) in that tablespace to store throw-away data/global variables that you'd like to share across sessions.
http://magazine.redhat.com/2007/12/12/tip-from-an-rhce-memory-storage-on-postgresql/
Advisory locks
These are documented in an obscure area of the manual:
http://www.postgresql.org/docs/9.0/interactive/functions-admin.html
It's occasionally faster than acquiring multitudes of row-level locks, and they can be used to work around cases where FOR UPDATE isn't implemented (such as recursive CTE queries).
This is my favorites list of lesser know features.
Transactional DDL
Nearly every SQL statement is transactional in Postgres. If you turn off autocommit the following is possible:
drop table customer_orders;
rollback;
select *
from customer_orders;
Range types and exclusion constraint
To my knowledge Postgres is the only RDBMS that lets you create a constraint that checks if two ranges overlap. An example is a table that contains product prices with a "valid from" and "valid until" date:
create table product_price
(
price_id serial not null primary key,
product_id integer not null references products,
price numeric(16,4) not null,
valid_during daterange not null
);
NoSQL features
The hstore extension offers a flexible and very fast key/value store that can be used when parts of the database need to be "schema-less". JSON is another option to store data in a schema-less fashion and
insert into product_price
(product_id, price, valid_during)
values
(1, 100.0, '[2013-01-01,2014-01-01)'),
(1, 90.0, '[2014-01-01,)');
-- querying is simply and can use an index on the valid_during column
select price
from product_price
where product_id = 42
and valid_during #> date '2014-10-17';
The execution plan for the above on a table with 700.000 rows:
Index Scan using check_price_range on public.product_price (cost=0.29..3.29 rows=1 width=6) (actual time=0.605..0.728 rows=1 loops=1)
Output: price
Index Cond: ((product_price.valid_during #> '2014-10-17'::date) AND (product_price.product_id = 42))
Buffers: shared hit=17
Total runtime: 0.772 ms
To avoid inserting rows with overlapping validity ranges a simple (and efficient) unique constraint can be defined:
alter table product_price
add constraint check_price_range
exclude using gist (product_id with =, valid_during with &&)
Infinity
Instead of requiring a "real" date far in the future Postgres can compare dates to infinity. E.g. when not using a date range you can do the following
insert into product_price
(product_id, price, valid_from, valid_until)
values
(1, 90.0, date '2014-01-01', date 'infinity');
Writeable common table expressions
You can delete, insert and select in a single statement:
with old_orders as (
delete from orders
where order_date < current_date - interval '10' year
returning *
), archived_rows as (
insert into archived_orders
select *
from old_orders
returning *
)
select *
from archived_rows;
The above will delete all orders older than 10 years, move them to the archived_orders table and then display the rows that were moved.
1.) When you need append notice to query, you can use nested comment
SELECT /* my comments, that I would to see in PostgreSQL log */
a, b, c
FROM mytab;
2.) Remove Trailing spaces from all the text and varchar field in a database.
do $$
declare
selectrow record;
begin
for selectrow in
select
'UPDATE '||c.table_name||' SET '||c.COLUMN_NAME||'=TRIM('||c.COLUMN_NAME||') WHERE '||c.COLUMN_NAME||' ILIKE ''% '' ' as script
from (
select
table_name,COLUMN_NAME
from
INFORMATION_SCHEMA.COLUMNS
where
table_name LIKE 'tbl%' and (data_type='text' or data_type='character varying' )
) c
loop
execute selectrow.script;
end loop;
end;
$$;
3.) We can use a window function for very effective removing of duplicate rows:
DELETE FROM tab
WHERE id IN (SELECT id
FROM (SELECT row_number() OVER (PARTITION BY column_with_duplicate_values), id
FROM tab) x
WHERE x.row_number > 1);
Some PostgreSQL's optimized version (with ctid):
DELETE FROM tab
WHERE ctid = ANY(ARRAY(SELECT ctid
FROM (SELECT row_number() OVER (PARTITION BY column_with_duplicate_values), ctid
FROM tab) x
WHERE x.row_number > 1));
4.) When we need to identify server's state, then we can use a function:
SELECT pg_is_in_recovery();
5.) Get functions's DDL command.
select pg_get_functiondef((select oid from pg_proc where proname = 'f1'));
6.) Safely changing column data type in PostgreSQL
create table test(id varchar );
insert into test values('1');
insert into test values('11');
insert into test values('12');
select * from test
--Result--
id
character varying
--------------------------
1
11
12
You can see from the above table that I have used the data type – ‘character varying’ for ‘id’
column. But it was a mistake, because I am always giving integers as id. So using varchar here is a
bad practice. So let’s try to change the column type to integer.
ALTER TABLE test ALTER COLUMN id TYPE integer;
But it returns:
ERROR: column “id” cannot be cast automatically to type integer SQL
state: 42804 Hint: Specify a USING expression to perform the
conversion
That means we can’t simply change the data type because data is already there in the column. Since the data is of type ‘character varying’ postgres cant expect it as integer though we entered integers only. So now, as postgres suggested we can use the ‘USING’ expression to cast our data into integers.
ALTER TABLE test ALTER COLUMN id TYPE integer USING (id ::integer);
It Works.
7.) Know who is connected to the Database
This is more or less a monitoring command. To know which user connected to which database
including their IP and Port use the following SQL:
SELECT datname,usename,client_addr,client_port FROM pg_stat_activity ;
8.) Reloading PostgreSQL Configuration files without Restarting Server
PostgreSQL configuration parameters are located in special files like postgresql.conf and pg_hba.conf. Often, you may need to change these parameters. But for some parameters to take effect we often need to reload the configuration file. Of course, restarting server will do it. But in a production environment it is not preferred to restarting the database, which is being used by thousands, just for setting some parameters. In such situations, we can reload the configuration files without restarting the server by using the following function:
select pg_reload_conf();
Remember, this wont work for all the parameters, some parameter
changes need a full restart of the server to be take in effect.
9.) Getting the data directory path of the current Database cluster
It is possible that in a system, multiple instances(cluster) of PostgreSQL is set up, generally, in different ports or so. In such cases, finding which directory(physical storage directory) is used by which instance is a hectic task. In such cases, we can use the following command in any database in the cluster of our interest to get the directory path:
SHOW data_directory;
The same function can be used to change the data directory of the cluster, but it requires a server restarts:
SET data_directory to new_directory_path;
10.) Find a CHAR is DATE or not
create or replace function is_date(s varchar) returns boolean as $$
begin
perform s::date;
return true;
exception when others then
return false;
end;
$$ language plpgsql;
Usage: the following will return True
select is_date('12-12-2014')
select is_date('12/12/2014')
select is_date('20141212')
select is_date('2014.12.12')
select is_date('2014,12,12')
11.) Change the owner in PostgreSQL
REASSIGN OWNED BY sa TO postgres;
12.) PGADMIN PLPGSQL DEBUGGER
Well explained here
It's convenient to rename an old database rather than mysql can do. Just using the following command:
ALTER DATABASE name RENAME TO new_name
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What are some hidden features of SQL Server?
For example, undocumented system stored procedures, tricks to do things which are very useful but not documented enough?
Answers
Thanks to everybody for all the great answers!
Stored Procedures
sp_msforeachtable: Runs a command with '?' replaced with each table name (v6.5 and up)
sp_msforeachdb: Runs a command with '?' replaced with each database name (v7 and up)
sp_who2: just like sp_who, but with a lot more info for troubleshooting blocks (v7 and up)
sp_helptext: If you want the code of a stored procedure, view & UDF
sp_tables: return a list of all tables and views of database in scope.
sp_stored_procedures: return a list of all stored procedures
xp_sscanf: Reads data from the string into the argument locations specified by each format argument.
xp_fixeddrives:: Find the fixed drive with largest free space
sp_help: If you want to know the table structure, indexes and constraints of a table. Also views and UDFs. Shortcut is Alt+F1
Snippets
Returning rows in random order
All database User Objects by Last Modified Date
Return Date Only
Find records which date falls somewhere inside the current week.
Find records which date occurred last week.
Returns the date for the beginning of the current week.
Returns the date for the beginning of last week.
See the text of a procedure that has been deployed to a server
Drop all connections to the database
Table Checksum
Row Checksum
Drop all the procedures in a database
Re-map the login Ids correctly after restore
Call Stored Procedures from an INSERT statement
Find Procedures By Keyword
Drop all the procedures in a database
Query the transaction log for a database programmatically.
Functions
HashBytes()
EncryptByKey
PIVOT command
Misc
Connection String extras
TableDiff.exe
Triggers for Logon Events (New in Service Pack 2)
Boosting performance with persisted-computed-columns (pcc).
DEFAULT_SCHEMA setting in sys.database_principles
Forced Parameterization
Vardecimal Storage Format
Figuring out the most popular queries in seconds
Scalable Shared Databases
Table/Stored Procedure Filter feature in SQL Management Studio
Trace flags
Number after a GO repeats the batch
Security using schemas
Encryption using built in encryption functions, views and base tables with triggers
In Management Studio, you can put a number after a GO end-of-batch marker to cause the batch to be repeated that number of times:
PRINT 'X'
GO 10
Will print 'X' 10 times. This can save you from tedious copy/pasting when doing repetitive stuff.
A lot of SQL Server developers still don't seem to know about the OUTPUT clause (SQL Server 2005 and newer) on the DELETE, INSERT and UPDATE statement.
It can be extremely useful to know which rows have been INSERTed, UPDATEd, or DELETEd, and the OUTPUT clause allows to do this very easily - it allows access to the "virtual" tables called inserted and deleted (like in triggers):
DELETE FROM (table)
OUTPUT deleted.ID, deleted.Description
WHERE (condition)
If you're inserting values into a table which has an INT IDENTITY primary key field, with the OUTPUT clause, you can get the inserted new ID right away:
INSERT INTO MyTable(Field1, Field2)
OUTPUT inserted.ID
VALUES (Value1, Value2)
And if you're updating, it can be extremely useful to know what changed - in this case, inserted represents the new values (after the UPDATE), while deleted refers to the old values before the UPDATE:
UPDATE (table)
SET field1 = value1, field2 = value2
OUTPUT inserted.ID, deleted.field1, inserted.field1
WHERE (condition)
If a lot of info will be returned, the output of OUTPUT can also be redirected to a temporary table or a table variable (OUTPUT INTO #myInfoTable).
Extremely useful - and very little known!
Marc
sp_msforeachtable: Runs a command with '?' replaced with each table name.
e.g.
exec sp_msforeachtable "dbcc dbreindex('?')"
You can issue up to 3 commands for each table
exec sp_msforeachtable
#Command1 = 'print ''reindexing table ?''',
#Command2 = 'dbcc dbreindex(''?'')',
#Command3 = 'select count (*) [?] from ?'
Also, sp_MSforeachdb
Connection String extras:
MultipleActiveResultSets=true;
This makes ADO.Net 2.0 and above read multiple, forward-only, read-only results sets on a single database connection, which can improve performance if you're doing a lot of reading. You can turn it on even if you're doing a mix of query types.
Application Name=MyProgramName
Now when you want to see a list of active connections by querying the sysprocesses table, your program's name will appear in the program_name column instead of ".Net SqlClient Data Provider"
TableDiff.exe
Table Difference tool allows you to discover and reconcile differences between a source and destination table or a view. Tablediff Utility can report differences on schema and data. The most popular feature of tablediff is the fact that it can generate a script that you can run on the destination that will reconcile differences between the tables.
Link
A less known TSQL technique for returning rows in random order:
-- Return rows in a random order
SELECT
SomeColumn
FROM
SomeTable
ORDER BY
CHECKSUM(NEWID())
In Management Studio, you can quickly get a comma-delimited list of columns for a table by :
In the Object Explorer, expand the nodes under a given table (so you will see folders for Columns, Keys, Constraints, Triggers etc.)
Point to the Columns folder and drag into a query.
This is handy when you don't want to use heinous format returned by right-clicking on the table and choosing Script Table As..., then Insert To... This trick does work with the other folders in that it will give you a comma-delimited list of names contained within the folder.
Row Constructors
You can insert multiple rows of data with a single insert statement.
INSERT INTO Colors (id, Color)
VALUES (1, 'Red'),
(2, 'Blue'),
(3, 'Green'),
(4, 'Yellow')
If you want to know the table structure, indexes and constraints:
sp_help 'TableName'
HashBytes() to return the MD2, MD4, MD5, SHA, or SHA1 hash of its input.
Figuring out the most popular queries
With sys.dm_exec_query_stats, you can figure out many combinations of query analyses by a single query.
Link
with the commnad
select * from sys.dm_exec_query_stats
order by execution_count desc
The spatial results tab can be used to create art.
enter link description here http://michaeljswart.com/wp-content/uploads/2010/02/venus.png
EXCEPT and INTERSECT
Instead of writing elaborate joins and subqueries, these two keywords are a much more elegant shorthand and readable way of expressing your query's intent when comparing two query results. New as of SQL Server 2005, they strongly complement UNION which has already existed in the TSQL language for years.
The concepts of EXCEPT, INTERSECT, and UNION are fundamental in set theory which serves as the basis and foundation of relational modeling used by all modern RDBMS. Now, Venn diagram type results can be more intuitively and quite easily generated using TSQL.
I know it's not exactly hidden, but not too many people know about the PIVOT command. I was able to change a stored procedure that used cursors and took 2 minutes to run into a speedy 6 second piece of code that was one tenth the number of lines!
useful when restoring a database for Testing purposes or whatever. Re-maps the login ID's correctly:
EXEC sp_change_users_login 'Auto_Fix', 'Mary', NULL, 'B3r12-36'
Drop all connections to the database:
Use Master
Go
Declare #dbname sysname
Set #dbname = 'name of database you want to drop connections from'
Declare #spid int
Select #spid = min(spid) from master.dbo.sysprocesses
where dbid = db_id(#dbname)
While #spid Is Not Null
Begin
Execute ('Kill ' + #spid)
Select #spid = min(spid) from master.dbo.sysprocesses
where dbid = db_id(#dbname) and spid > #spid
End
Table Checksum
Select CheckSum_Agg(Binary_CheckSum(*)) From Table With (NOLOCK)
Row Checksum
Select CheckSum_Agg(Binary_CheckSum(*)) From Table With (NOLOCK) Where Column = Value
I'm not sure if this is a hidden feature or not, but I stumbled upon this, and have found it to be useful on many occassions. You can concatonate a set of a field in a single select statement, rather than using a cursor and looping through the select statement.
Example:
DECLARE #nvcConcatonated nvarchar(max)
SET #nvcConcatonated = ''
SELECT #nvcConcatonated = #nvcConcatonated + C.CompanyName + ', '
FROM tblCompany C
WHERE C.CompanyID IN (1,2,3)
SELECT #nvcConcatonated
Results:
Acme, Microsoft, Apple,
If you want the code of a stored procedure you can:
sp_helptext 'ProcedureName'
(not sure if it is hidden feature, but I use it all the time)
A stored procedure trick is that you can call them from an INSERT statement. I found this very useful when I was working on an SQL Server database.
CREATE TABLE #toto (v1 int, v2 int, v3 char(4), status char(6))
INSERT #toto (v1, v2, v3, status) EXEC dbo.sp_fulubulu(sp_param1)
SELECT * FROM #toto
DROP TABLE #toto
In SQL Server 2005/2008 to show row numbers in a SELECT query result:
SELECT ( ROW_NUMBER() OVER (ORDER BY OrderId) ) AS RowNumber,
GrandTotal, CustomerId, PurchaseDate
FROM Orders
ORDER BY is a compulsory clause. The OVER() clause tells the SQL Engine to sort data on the specified column (in this case OrderId) and assign numbers as per the sort results.
Useful for parsing stored procedure arguments: xp_sscanf
Reads data from the string into the argument locations specified by each format argument.
The following example uses xp_sscanf
to extract two values from a source
string based on their positions in the
format of the source string.
DECLARE #filename varchar (20), #message varchar (20)
EXEC xp_sscanf 'sync -b -fproducts10.tmp -rrandom', 'sync -b -f%s -r%s',
#filename OUTPUT, #message OUTPUT
SELECT #filename, #message
Here is the result set.
-------------------- --------------------
products10.tmp random
Return Date Only
Select Cast(Floor(Cast(Getdate() As Float))As Datetime)
or
Select DateAdd(Day, 0, DateDiff(Day, 0, Getdate()))
dm_db_index_usage_stats
This allows you to know if data in a table has been updated recently even if you don't have a DateUpdated column on the table.
SELECT OBJECT_NAME(OBJECT_ID) AS DatabaseName, last_user_update,*
FROM sys.dm_db_index_usage_stats
WHERE database_id = DB_ID( 'MyDatabase')
AND OBJECT_ID=OBJECT_ID('MyTable')
Code from: http://blog.sqlauthority.com/2009/05/09/sql-server-find-last-date-time-updated-for-any-table/
Information referenced from:
SQL Server - What is the date/time of the last inserted row of a table?
Available in SQL 2005 and later
Here are some features I find useful but a lot of people don't seem to know about:
sp_tables
Returns a list of objects that can be
queried in the current environment.
This means any object that can appear
in a FROM clause, except synonym
objects.
Link
sp_stored_procedures
Returns a list of stored procedures in
the current environment.
Link
Find records which date falls somewhere inside the current week.
where dateadd( week, datediff( week, 0, TransDate ), 0 ) =
dateadd( week, datediff( week, 0, getdate() ), 0 )
Find records which date occurred last week.
where dateadd( week, datediff( week, 0, TransDate ), 0 ) =
dateadd( week, datediff( week, 0, getdate() ) - 1, 0 )
Returns the date for the beginning of the current week.
select dateadd( week, datediff( week, 0, getdate() ), 0 )
Returns the date for the beginning of last week.
select dateadd( week, datediff( week, 0, getdate() ) - 1, 0 )
Not so much a hidden feature but setting up key mappings in Management Studio under Tools\Options\Keyboard:
Alt+F1 is defaulted to sp_help "selected text" but I cannot live without the adding Ctrl+F1 for sp_helptext "selected text"
Persisted-computed-columns
Computed columns can help you shift the runtime computation cost to data modification phase. The computed column is stored with the rest of the row and is transparently utilized when the expression on the computed columns and the query matches. You can also build indexes on the PCC’s to speed up filtrations and range scans on the expression.
Link
There are times when there's no suitable column to sort by, or you just want the default sort order on a table and you want to enumerate each row. In order to do that you can put "(select 1)" in the "order by" clause and you'd get what you want. Neat, eh?
select row_number() over (order by (select 1)), * from dbo.Table as t
Simple encryption with EncryptByKey