I have messed up the data. I have been ammended ids and values to the point where i cannot remember what the originals were. (testing a few things).
I have a table called query_string_interpretation and its part of the DB called, test1_db
I have a backup database which i have restored called, test2_db
How can I restore its contents from one database table to another?
Without more information on your part...generally you can use INSERT INTO/SELECT FROM to move data between tables.
The syntax is roughly:
INSERT INTO
test1_db..query_string_interpretation ( <your columns here>)
select <your columns here>
FROM test2_db..query_string_interpretation
At first, you need to be sure that you have all your data in source table, or data is placed in both tables - source and destination. In first case you need to truncate the destination table:
TRUNCATE TABLE test1_db..query_string_interpretation
Second, you need to be sure that you will insert the right values into IDENTITY fields, if these fields exists. Use SET INDENITY_INSERT ON statement.
Third, you need to insert the values:
insert into test1_db..query_string_interpretation
select * from test2_db..query_string_interpretation
And don't forget to switch the INDENITY_INSERT to OFF, you you switched it to ON in the second step.
You can use a SQL wizard to do this for you. In Management Studio, right click on either database, select Tasks then Import Data... or Export Data...
try this:
delete from test1_db..query_string_interpretation
insert into test1_db..query_string_interpretation
select * from test2_db..query_string_interpretation
if you have an identity field you may have to write the name of the columns (except for the identity one). if you need to keep the IDs, take a look at the SET IDENTITY_INSERT ON statement here
Related
I need to make a provisionary table (TAB_PROV). This table will have its origin in a main table (TAB_MAIN). I need everything from the main table, except the data (rows).
I searched for some examples and none of them worked for me
CREATE TABLE TAB_PROV LIKE TAB_MAIN
CREATE TABLE TAB_PROV AS TAB_MAIN
You can just simply do:
SELECT *
FROM TAB_MAIN
INTO TAB_PROV
WHERE 1 = 2
Since the WHERE condition will never be true, no data is ever copied - but the table structure is replicated - TAB_PROV is created and has the same column as TAB_MAIN. This does NOT however copy any constraints (check or default constraints) or triggers over - it only recreates the columns (and their datatypes).
If you want a real and complete "copy" of your table, then you should use the "Script Table" function in SSMS to get the SQL needed for TAB_MAIN and then adapt it to create TAB_PROV from it.
In SQL Server Management Studio, you can right-click the table and select
Script Table as -> Create To -> New Query Editor Window
This will create just the table creation script for you.
You can also try the code below but it will copy everything.
SELECT *
INTO NewTable
FROM OldTable
TRUNCATE TABLE NewTable
I have situation where I need to change the order of the columns/adding new columns for existing Table in SQL Server 2008.
Existing column
MemberName
MemberAddress
Member_ID(pk)
and I want this order
Member_ID(pk)
MemberName
MemberAddress
I got the answer for the same ,
Go on SQL Server → Tools → Options → Designers → Table and Database Designers and unselect Prevent saving changes that require table re-creation
2- Open table design view and that scroll your column up and down and save your changes.
It is not possible with ALTER statement. If you wish to have the columns in a specific order, you will have to create a newtable, use INSERT INTO newtable (col-x,col-a,col-b) SELECT col-x,col-a,col-b FROM oldtable to transfer the data from the oldtable to the newtable, delete the oldtable and rename the newtable to the oldtable name.
This is not necessarily recommended because it does not matter which order the columns are in the database table. When you use a SELECT statement, you can name the columns and have them returned to you in the order that you desire.
If your table doesn't have any records you can just drop then create your table.
If it has records you can do it using your SQL Server Management Studio.
Just click your table > right click > click Design then you can now arrange the order of the columns by dragging the fields on the order that you want then click save.
Best Regards
I tried this and dont see any way of doing it.
here is my approach for it.
Right click on table and Script table for Create and have this on
one of the SQL Query window,
EXEC sp_rename 'Employee', 'Employee1' -- Original table name is Employee
Execute the Employee create script, make sure you arrange the columns in the way you need.
INSERT INTO TABLE2 SELECT * FROM TABLE1.
-- Insert into Employee select Name, Company from Employee1
DROP table Employee1.
Relying on column order is generally a bad idea in SQL. SQL is based on Relational theory where order is never guaranteed - by design. You should treat all your columns and rows as having no order and then change your queries to provide the correct results:
For Columns:
Try not to use SELECT *, but instead specify the order of columns in the select list as in: SELECT Member_ID, MemberName, MemberAddress from TableName. This will guarantee order and will ease maintenance if columns get added.
For Rows:
Row order in your result set is only guaranteed if you specify the ORDER BY clause.
If no ORDER BY clause is specified the result set may differ as the Query Plan might differ or the database pages might have changed.
Hope this helps...
This can be an issue when using Source Control and automated deployments to a shared development environment. Where I work we have a very large sample DB on our development tier to work with (a subset of our production data).
Recently I did some work to remove one column from a table and then add some extra ones on the end. I then had to undo my column removal so I re-added it on the end which means the table and all references are correct in the environment but the Source Control automated deployment will no longer work because it complains about the table definition changing.
The real problem here is that the table + indexes are ~120GB and the environment only has ~60GB free so I'll need to either:
a) Rename the existing columns which are in the wrong order, add new columns in the right order, update the data then drop the old columns
OR
b) Rename the table, create a new table with the correct order, insert to the new table from the old and delete from the old as I go along
The SSMS/TFS Schema compare option of using a temp table won't work because there isn't enough room on disc to do it.
I'm not trying to say this is the best way to go about things or that column order really matters, just that I have a scenario where it is an issue and I'm sharing the options I've thought of to fix the issue
SQL query to change the id column into first:
ALTER TABLE `student` CHANGE `id` `id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT FIRST;
or by using:
ALTER TABLE `student` CHANGE `id` `id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT AFTER 'column_name'
What is the difference between using
SELECT ... INTO MyTable FROM...
and
INSERT INTO MyTable (...)
SELECT ... FROM ....
?
From BOL [ INSERT, SELECT...INTO ], I know that using SELECT...INTO will create the insertion table on the default file group if it doesn't already exist, and that the logging for this statement depends on the recovery model of the database.
Which statement is preferable?
Are there other performance implications?
What is a good use case for SELECT...INTO over INSERT INTO ...?
Edit: I already stated that I know that that SELECT INTO... creates a table where it doesn't exist. What I want to know is that SQL includes this statement for a reason, what is it? Is it doing something different behind the scenes for inserting rows, or is it just syntactic sugar on top of a CREATE TABLE and INSERT INTO.
They do different things. Use INSERT when the table exists. Use SELECT INTO when it does not.
Yes. INSERT with no table hints is normally logged. SELECT INTO is minimally logged assuming proper trace flags are set.
In my experience SELECT INTO is most commonly used with intermediate data sets, like #temp tables, or to copy out an entire table like for a backup. INSERT INTO is used when you insert into an existing table with a known structure.
EDIT
To address your edit, they do different things. If you are making a table and want to define the structure use CREATE TABLE and INSERT. Example of an issue that can be created: You have a small table with a varchar field. The largest string in your table now is 12 bytes. Your real data set will need up to 200 bytes. If you do SELECT INTO from your small table to make a new one, the later INSERT will fail with a truncation error because your fields are too small.
Which statement is preferable? Depends on what you are doing.
Are there other performance implications? If the table is a permanent table, you can create indexes at the time of table creation which has implications for performance both negatively and positiviely. Select into does not recreate indexes that exist on current tables and thus subsequent use of the table may be slower than it needs to be.
What is a good use case for SELECT...INTO over INSERT INTO ...? Select into is used if you may not know the table structure in advance. It is faster to write than create table and an insert statement, so it is used to speed up develoment at times. It is often faster to use when you are creating a quick temp table to test things or a backup table of a specific query (maybe records you are going to delete). It should be rare to see it used in production code that will run multiple times (except for temp tables) because it will fail if the table was already in existence.
It is sometimes used inappropriately by people who don't know what they are doing. And they can cause havoc in the db as a result. I strongly feel it is inappropriate to use SELECT INTO for anything other than a throwaway table (a temporary backup, a temp table that will go away at the end of the stored proc ,etc.). Permanent tables need real thought as to their design and SELECT INTO makes it easy to avoid thinking about anything even as basic as what columns and what datatypes.
In general, I prefer the use of the create table and insert statement - you have more controls and it is better for repeatable processes. Further, if the table is a permanent table, it should be created from a separate create table script (one that is in source control) as creating permanent objects should not, in general, in code are inserts/deletes/updates or selects from a table. Object changes should be handled separately from data changes because objects have implications beyond the needs of a specific insert/update/select/delete. You need to consider the best data types, think about FK constraints, PKs and other constraints, consider auditing requirements, think about indexing, etc.
Each statement has a distinct use case. They are not interchangeable.
SELECT...INTO MyTable... creates a new MyTable where one did not exist before.
INSERT INTO MyTable...SELECT... is used when MyTable already exists.
The primary difference is that SELECT INTO MyTable will create a new table called MyTable with the results, while INSERT INTO requires that MyTable already exists.
You would use SELECT INTO only in the case where the table didn't exist and you wanted to create it based on the results of your query. As such, these two statements really are not comparable. They do very different things.
In general, SELECT INTO is used more often for one off tasks, while INSERT INTO is used regularly to add rows to tables.
EDIT:
While you can use CREATE TABLE and INSERT INTO to accomplish what SELECT INTO does, with SELECT INTO you do not have to know the table definition beforehand. SELECT INTO is probably included in SQL because it makes tasks like ad hoc reporting or copying tables much easier.
Actually SELECT ... INTO not only creates the table but will fail if it already exists, so basically the only time you would use it is when the table you are inserting to does not exists.
In regards to your EDIT:
I personally mainly use SELECT ... INTO when I am creating a temp table. That to me is the main use. However I also use it when creating new tables with many columns with similar structures to other tables and then edit it in order to save time.
I only want to cover second point of the question that is related to performance, because no body else has covered this. Select Into is a lot more faster than insert into, when it comes to tables with large datasets. I prefer select into when I have to read a very large table. insert into for a table with 10 million rows may take hours while select into will do this in minutes, and as for as losing indexes on new table is concerned you can recreate the indexes by query and can still save a lot more time when compared to insert into.
SELECT INTO is typically used to generate temp tables or to copy another table (data and/or structure).
In day to day code you use INSERT because your tables should already exist to be read, UPDATEd, DELETEd, JOINed etc. Note: the INTO keyword is optional with INSERT
That is, applications won't normally create and drop tables as part of normal operations unless it is a temporary table for some scope limited and specific usage.
A table created by SELECT INTO will have no keys or indexes or constraints unlike a real, persisted, already existing table
The 2 aren't directly comparable because they have almost no overlap in usage
Select into creates new table for you at the time and then insert records in it from the source table. The newly created table has the same structure as of the source table.If you try to use select into for a existing table it will produce a error, because it will try to create new table with the same name.
Insert into requires the table to be exist in your database before you insert rows in it.
The simple difference between select Into and Insert Into is:
--> Select Into don't need existing table. If you want to copy table A data, you just type Select * INTO [tablename] from A. Here, tablename can be existing table or new table will be created which has same structure like table A.
--> Insert Into do need existing table.INSERT INTO [tablename] SELECT * FROM A;.
Here tablename is an existing table.
Select Into is usually more popular to copy data especially backup data.
You can use as per your requirement, it is totally developer choice which should be used in his scenario.
Performance wise Insert INTO is fast.
References :
https://www.w3schools.com/sql/sql_insert_into_select.asp
https://www.w3schools.com/sql/sql_select_into.asp
The other answers are all great/correct (the main difference is whether the DestTable exists already (INSERT), or doesn't exist yet (SELECT ... INTO))
You may prefer to use INSERT (instead of SELECT ... INTO), if you want to be able to COUNT(*) the rows that have been inserted so far.
Using SELECT COUNT(*) ... WITH NOLOCK is a simple/crude technique that may help you check the "progress" of the INSERT; helpful if it's a long-running insert, as seen in this answer).
[If you use...]
INSERT DestTable SELECT ... FROM SrcTable
...then your SELECT COUNT(*) from DestTable WITH (NOLOCK) query would work.
Select into for large datasets may be good only for a single user using one single connection to the database doing a bulk operation task. I do not recommend to use
SELECT * INTO table
as this creates one big transaction and creates schema lock to create the object, preventing other users to create object or access system objects until the SELECT INTO operation completes.
As proof of concept open 2 sessions, in first session try to use
select into temp table from a huge table
and in the second section try to
create a temp table
and check the locks, blocking and the duration of second session to create a temp table object. My recommendation it is always a good practice to create and Insert statement and if needed for minimal logging use trace flag 610.
I would like to have a column in my DB accessible via two column names temporarily.
Why? The column name was badly chosen, I would like to refactor it. As I want my webapp to remain stable while changing the column name, it would be good to
have a (let's call it) symlink named better_column_name pointing to the column bad_column_name
change the webapplication to use better_column_name
drop the symlink and rename column to better_column_name
"Refactoring Databases" suggests to actually add a second column which is synchronized on commit in order to achieve this. I am just hoping that there might be an easier way with Oracle, with less work and less overhead.
As long as you have code that uses both column names, I don't see a way to get around the fact that you'll have two (real) columns in that table.
I would add the new column with the correct name and then create a trigger that checks which column has been modified and updates the "other" column correspondingly. So whatever is being updated, the value is synch'ed with the other column.
Once all the code that uses the old column has been migrated, remove the trigger and drop the old column.
Edit
The trigger would so do something like this:
CREATE OR REPLACE TRIGGER ...
...
UPDATE OF bad_column_name, better_column_name ON the_table
...
BEGIN
IF UPDATING ('BAD_COLUMN_NAME') THEN
:new.better_column_name = :new.bad_column_name
END IF;
IF UPDATING ('BETTER_COLUMN_NAME') THEN
:new.bad_column_name = :new.better_column_name
END IF;
END;
The order of the IF statements controls which change has a "higher priority" in case someone updated both columns at the same time.
Rename the table:
alter table mytable rename to mytable_old;
Create a view with the original tablename with both bad_column_name and better_column_name that point to the same column (and of course all the other columns):
create or replace view mytable as
select column1
, column2
, ...
, bad_column_name
, bad_column_name better_column_name
from mytable_old
;
Since this view is updatable by default (I assume here that mytable has a primary key), you can insert/update/delete from the view and it doesn't matter if you use bad_column_name or better_column_name.
After the refactoring, drop the view and rename the table and column:
drop view mytable;
alter table mytable_old rename column bad_column_name to better_column_name;
alter table mytable_old rename to mytable;
The best solution to this is only available in Oracle 11g Release 2: Edition-based Redefinition. This really cool feature allows us to maintain different versions of database tables and PL/SQL code, using special triggers and views. Find out more.
Essentially this is Oracle's built-in implementation of #AHorseWithNoName's suggestion.
you can create a view for the table. And port your application to use that view instead of the table.
create table t (bad_name varchar2(10), c2 varchar2(10));
create view vt as select bad_name AS good_name, c2 from t;
insert into vt (good_name, c2) values ('blub', 'blob');
select * from t;
select * from vt;
If you're on 11g you could look at using a virtual column. I'd probably be tempted to change the order slightly; rename the real column and create the virtual one using the old (bad) name, which can then be dropped at leisure. You may be restricted, of course, and there may be implications on other objects being invalidated that make this order less suitable for you.
I am working with SQL Server (I am a SQL Server noob) and trying to alter a table. I want to CREATE TABLE LIKE to safely store data while I drop keys and constraints and all the other rigamorole that SQL Server seems to require when altering on the original table but I have not been able to find a match to that command...
you want to recreate the same structure?
how about this
SELECT *
into test
FROM myRealTable
where 0=1
no data will be inserted into the new table
You can do
SELECT * INTO #MyTable_tmp FROM MyTable
Then modify your MyTable, and copy your data back in. Other approaches I've seen is to create a new table call it Mytable_Tmp (Not a temp table), which will be your new table.
Then copy your data doing any migrations you need. Then you will drop the original table and do a rename on Mytable.
Or you can get one of the many excellant tools that compare databases and generate difference scripts or VSTS DB Edition (Comes with developer) and you can do a diff script from a project file to a DB.
Edit
When you run SELECT * INTO #MyTable FROM MyTable, SQL Server creates a new temporary table called #MyTable that matches each column and data type from your select clause. In this case we are selecting * so it will match MyTable. This only creates the columns it doesn't copy defaults, constraints indexes or anything else.