Currently exploring different ways to identify deltas. I've got something using a change capture stream, but wanted to get something working on a table with change tracking enabled as an alternative option.
This is what I attempted to do:
create or replace table T1 (
id number(8) not null,
c1 varchar(255) default null
);
create or replace table T1_MERGED_OUTPUT (
id number(8) not null,
c1 varchar(255) default null
);
create or replace table DELTA_UPDATE_TIMES (
id number(8) not null,
table_name varchar(255) not null,
last_update_datetime TIMESTAMP_TZ default current_timestamp()
);
alter table t1 set change_tracking = true;
T1 is the source table with change tracking enabled. T1_MERGED_OUTPUT will be loaded with the incremental updates. DELTA_UPDATE_TIMES holds the times of when each table was updated. To get the latest update timestamps for each table, I've defined a UDF:
CREATE OR REPLACE FUNCTION TABLE_LAST_UPDATE_DATETIME(tbl VARCHAR)
RETURNS TIMESTAMP_TZ
AS
$$
SELECT MAX(LASTEST_UPDATE_DATETIME) FROM DELTA_UPDATE_TIMES WHERE TABLE_NAME = tbl
$$;
Then I tried to create another UDF to get the changes between the last update time and the current time like this:
CREATE OR REPLACE FUNCTION DATA_LAST_UPDATE_DATETIME(start_time TIMESTAMP_TZ)
RETURNS TABLE(ID NUMBER, C1 VARCHAR, ACTION_NAME VARCHAR, IS_UPDATE BOOLEAN)
AS
$$
select ID, C1, METADATA$ACTION AS ACTION_NAME, METADATA$ISUPDATE AS IS_UPDATE
from t1
changes(information => default)
at(timestamp => start_time)
end(timestamp => current_timestamp())
$$;
But I'm getting this error: SQL compilation error: error line 2 at position 29 invalid identifier 'METADATA$ACTION'
When I run that query outside of the function, it works correct and the action and is_update is returned.
Any ideas what the issue is here and whether there is a way round it?
Related
I need to update an existing table by adding a new column with default value as UUID and datatype as VARCHAR(255).
I tried to achieved it by writing a function as:
CREATE FUNCTION UUID_FUNC()
RETURNS VARCHAR(255)
LANGUAGE SQL
BEGIN ATOMIC
DECLARE UUID VARCHAR(4000);
SET UUID = (SELECT TRIM(CHAR(HEX(GENERATE_UNIQUE()))) from sysibm.sysdummy1);
RETURN UUID;
END
And used it in the query as:
ALTER TABLE <Table-name>
ADD ID_VALUE VARCHAR(255) NOT NULL DEFAULT (UUID_FUNC())
Got following error when executing the above query:
SQL Error [42601]: An unexpected token "DEFAULT" was found following "ARCHAR(255) NOT NULL".
Expected tokens may include: "CHECK".. SQLCODE=-104, SQLSTATE=42601, DRIVER=3.59.81
What is the correct format for calling custom defined functions in ALTER query or any suggestions to achieve the above requirement is appreciated.
Thanks in advance.
I was able to achieve it in following way:
ALTER TABLE <Table-name> ADD ID_VALUE VARCHAR(255) NOT NULL DEFAULT '0';
UPDATE <Table-name> SET ID_VALUE=(hex(GENERATE_UNIQUE())) WHERE ID_VALUE='0';
You would need to do this via a trigger, rather than as a generated expression. Given the DDL:
create or replace function your.uuid_func()
returns char(26)
language sql
not deterministic
return values(hex(generate_unique()));
create table your.table (
c1 int not null,
c2 char(26) not null
);
You can create the trigger:
create trigger set_uuid
before insert on your.table
referencing new as n
for each row
when (n.id_value is null)
set n.id_value = your.uuid_func();
Then the insert:
—- You can insert a normal string:
insert into your.table (c1, c2)
values (1, ‘anything’);
—- Or, if you don’t provide a value for c2, it will be set
—- to the value of UUID_FUNC():
insert into your.table (c1)
values (2);
Results:
select * from your.table;
C1 C2
----------- --------------------------
1 anything
2 20200111154913255440000000
ALTER TABLE ADD ID_VALUE AS (UUID_FUNC());
For accessing existing field values,
ALTER TABLE ADD ID_VALUE AS (UUID_FUNC([field_name]));
i want to make column Customers_Balance on TBL_CUSTOMERS to show by defult the result of that stored procedures....
TBL_CUSTOMERS which it have the info of the customer, and it created as like that
CREATE TABLE TBL_CUSTOMERS
(
Customers_ID int PRIMARY KEY,
Customers_Name varchar(100) NOT NULL,
Customers_Phone varchar(100),
Customers_Address varchar(100),
Customers_Web varchar(100),
Customers_Balance decimal(16,0) not null,
);
TBL_CUSTOMERS_DETAILS which it have the details of all customer transactions , and it created as like that
CREATE TABLE TBL_CUSTOMERS_DETAILS
(
Customers_Details_ID int PRIMARY KEY,
Customers_ID int,
Customers_Details_Tybe varchar(50) not null,
Customers_Details_Date date not null,
Customers_Details_Amount decimal(16,0) not null,
);
i have created stored procedures to calculate the result of sum of customer's transactions balance and worked fine, and it created as like that
CREATE PROC SP_SUM_CUSTOMERS_DETAILS_AMOUNT
#ID INT
AS
SELECT SUM(Customers_Details_Amount)
FROM TBL_CUSTOMERS_DETAILS
Where Customers_ID = #ID
NOW
i want to make column Customers_Balance on TBL_CUSTOMERS to show by defult the result of that stored procedures....
how i can make something like that ??
Materializing values that can be calculated by other materialize values is usually a bad idea as it bears the risk of inconsistencies.
So you best drop the column Customers_Balance in TBL_CUSTOMERS and the procedure and then create a view which includes the customer's data and their balance. You can do so by a join and aggregation.
ALTER TABLE TBL_CUSTOMERS
DROP COLUMN Customers_Balance;
DROP PROCEDURE SP_SUM_CUSTOMERS_DETAILS_AMOUNT;
CREATE VIEW VW_CUSTOMERS
AS
SELECT C.Customers_ID,
C.Customers_Name,
C.Customers_Phone,
C.Customers_Address,
C.Customers_Web,
sum(CD.Customers_Details_Amount) Customers_Balance
FROM TBL_CUSTOMERS C
INNER JOIN TBL_CUSTOMERS_DETAILS CD
ON CD.Customers_ID = C.Customers_ID
GROUP BY C.Customers_ID,
C.Customers_Name,
C.Customers_Phone,
C.Customers_Address,
C.Customers_Web;
You are looking for a Computed Column
What you need to do is to create a scalar function rather than a stored procedure (simply change your current stored procedure into a scalar function), and then use this function in your computed column. This would give you an auto-updated results on your computed column.
So, redoing your work should be something like this :
-- CREATE THE SCALAR FUNCTION FIRST
CREATE FUNCTION SUM_CUSTOMERS_DETAILS_AMOUNT (#ID INT)
RETURNS INT
AS
BEGIN
RETURN (
SELECT SUM(Customers_Details_Amount)
FROM TBL_CUSTOMERS_DETAILS
WHERE Customers_ID = #ID
)
END
GO
-- NOW DROP THE CURRENT Customers_Balance COLUMN
ALTER TABLE TBL_CUSTOMERS
DROP COLUMN Customers_Balance
GO
-- CREATE THE COMPUTED COLUMN WITH THE FUNCTION
ALTER TABLE TBL_CUSTOMERS
ADD Customers_Balance AS dbo.SUM_CUSTOMERS_DETAILS_AMOUNT (Customers_ID)
GO
In my SQL Server 2012 environment, I've created a series of stored procedures that pass pre-existing temporary tables among themselves (I have tried different architectures here, but wasn't able to bypass this due to the nature of the requirements / procedures).
What I'm trying to do is to, within a stored procedure check if a temporary table has already been created and, if not, to create it.
My current SQL looks as follows:
IF OBJECT_ID('tempdb..#MyTable') IS NULL
CREATE TABLE #MyTable
(
Col1 INT,
Col2 VARCHAR(10)
...
);
But when I try and run it when the table already exists, I get the error message
There is already an object named '#MyTable' in the database
So it seems it doesn't simply ignore those lines within the If statement.
Is there a way to accomplish this - create a temp table if it doesn't already exist, otherwise, use the one already in memory?
Thanks!
UPDATE:
For whatever reason, following #RaduGheorghiu's suggestion from the comments, I found out that the system creates a temporary table with a name along the lines of dbo.#MyTable________________________________________________0000000001B1
Is that why I can't find it? Is there any way to change that? This is new to me....
Following the link here, http://weblogs.sqlteam.com/mladenp/archive/2008/08/21/SQL-Server-2005-temporary-tables-bug-feature-or-expected-behavior.aspx
It seems as though you need to use the GO statement.
You meant to use IS NOT NULL i think... this is commonly used to clear temp tables so you don't get the error you mentioned in your OP.
IF OBJECT_ID('tempdb..#MyTable') IS NOT NULL DROP TABLE #MyTable
CREATE TABLE #MyTable
(
Col1 INT,
Col2 VARCHAR(10)
);
The big difference is the DROP TABLE statement after you do your logical check. Also, creating your table without filling data doesn't make it NULL
DROP TABLE #MyTable
CREATE TABLE #MyTable
(
Col1 INT,
Col2 VARCHAR(10)
);
IF OBJECT_ID('tempdb..#MyTable') IS NOT NULL
SELECT 1
Try wrapping your actions in a begin...end block:
if object_id('tempdb..#MyTable') is null
begin
create table #MyTable (
Col1 int
, Col2 varchar(10)
);
end
This seems odd, but it works when I try it
IF(OBJECT_ID('tempdb..#Test') IS NULL) --check if it exists
BEGIN
IF(1 = 0)--this will never actually run, but it tricks the parser into allowing the CREATE to run
DROP TABLE #Test;
PRINT 'Create table';
CREATE TABLE #Test
(
ID INT NOT NULL PRIMARY KEY
);
END
IF(NOT EXISTS(SELECT 1 FROM #Test))
INSERT INTO #Test(ID)
VALUES(1);
SELECT *
FROM #Test;
--Try dropping the table and test again
--DROP TABLE #Test;
I have a table access whose schema is as below:
create table access (
access_id int primary key identity,
access_name varchar(50) not null,
access_time datetime2 not null default (getdate()),
access_type varchar(20) check (access_type in ('OUTER_PARTY','INNER_PARTY')),
access_message varchar(100) not null,
)
Access types allowed are only OUTER_PARTY and INNER_PARTY.
What I am trying to achieve is that the INNER_PARTY entry should be only once per day per login (user), but the OUTER_PARTY can be recorded any number of times. So I was wondering if its possible to do it directly or if there is an idiom to create this kind of restriction.
I have checked this question: Combining the UNIQUE and CHECK constraints, but was not able to apply it to my situation as it was aiming for a different thing.
A filtered unique index can be added to the table. This index can be based on a computed column which removes the time component from the access_time column.
create table access (
access_id int primary key identity,
access_name varchar(50) not null,
access_time datetime2 not null default (SYSDATETIME()),
access_type varchar(20) check (access_type in ('OUTER_PARTY','INNER_PARTY')),
access_message varchar(100) not null,
access_date as CAST(access_time as date)
)
go
create unique index IX_access_singleinnerperday on access (access_date,access_name) where access_type='INNER_PARTY'
go
Seems to work:
--these inserts are fine
insert into access (access_name,access_type,access_message)
select 'abc','inner_party','hello' union all
select 'def','outer_party','world'
go
--as are these
insert into access (access_name,access_type,access_message)
select 'abc','outer_party','hello' union all
select 'def','outer_party','world'
go
--but this one fails
insert into access (access_name,access_type,access_message)
select 'abc','inner_party','hello' union all
select 'def','inner_party','world'
go
unfortunately you cant add a "if" on a check constraint. I advise using a trigger:
create trigger myTrigger
on access
instead of insert
as
begin
declare #access_name varchar(50)
declare #access_type varchar(20)
declare #access_time datetime2
select #access_name = access_name, #access_type= access_type, #access_time=access_time from inserted
if exists (select 1 from access where access_name=#access_name and access_type=#access_type and access_time=#access_time) begin
--raise excetion
end else begin
--insert
end
end
you will have to format the #access_time to consider only the date part
I want the code to be able to automatically update the time stamp when a new row is inserted as I can do in MySQL using CURRENT_TIMESTAMP.
How will I be able to achieve this in PostgreSQL?
CREATE TABLE users (
id serial not null,
firstname varchar(100),
middlename varchar(100),
lastname varchar(100),
email varchar(200),
timestamp timestamp
)
To populate the column during insert, use a DEFAULT value:
CREATE TABLE users (
id serial not null,
firstname varchar(100),
middlename varchar(100),
lastname varchar(100),
email varchar(200),
timestamp timestamp default current_timestamp
)
Note that the value for that column can explicitly be overwritten by supplying a value in the INSERT statement. If you want to prevent that you do need a trigger.
You also need a trigger if you need to update that column whenever the row is updated (as mentioned by E.J. Brennan)
Note that using reserved words for column names is usually not a good idea. You should find a different name than timestamp
You'll need to write an insert trigger, and possible an update trigger if you want it to change when the record is changed. This article explains it quite nicely:
http://www.revsys.com/blog/2006/aug/04/automatically-updating-a-timestamp-column-in-postgresql/
CREATE OR REPLACE FUNCTION update_modified_column()
RETURNS TRIGGER AS $$
BEGIN
NEW.modified = now();
RETURN NEW;
END;
$$ language 'plpgsql';
Apply the trigger like this:
CREATE TRIGGER update_customer_modtime BEFORE UPDATE ON customer FOR EACH ROW EXECUTE PROCEDURE update_modified_column();
Updating timestamp, only if the values changed
Based on E.J's link and add a if statement from this link (https://stackoverflow.com/a/3084254/1526023)
CREATE OR REPLACE FUNCTION update_modified_column()
RETURNS TRIGGER AS $$
BEGIN
IF row(NEW.*) IS DISTINCT FROM row(OLD.*) THEN
NEW.modified = now();
RETURN NEW;
ELSE
RETURN OLD;
END IF;
END;
$$ language 'plpgsql';
Using 'now()' as default value automatically generates time-stamp.
To automatically update the timestamp field in PostgresSQL whenever a new row is inserted, you can set the current_timestamp as its default value:
CREATE TABLE users (
id serial not null,
firstname varchar(100),
middlename varchar(100),
lastname varchar(100),
email varchar(200),
timestamp timestamp default current_timestamp
)
In addition to this, you might want to prevent anyone from updating this field in the future, and this can be done by creating an update trigger and applying it:
CREATE OR REPLACE FUNCTION stop_change_on_timestamp()
RETURNS trigger AS
$BODY$
BEGIN
-- always reset the timestamp to the old value ("actual creation time")
NEW.timestamp := OLD.timestamp;
RETURN NEW;
END;
$BODY$
CREATE TRIGGER prevent_timestamp_changes
BEFORE UPDATE
ON users
FOR EACH ROW
EXECUTE PROCEDURE stop_change_on_timestamp();
For update and Liquibase YAML:
databaseChangeLog:
- changeSet:
id: CREATE FUNCTION set_now_to_timestamp
author: Konstantin Chvilyov
changes:
- sql:
sql: CREATE OR REPLACE FUNCTION set_now_to_timestamp() RETURNS TRIGGER LANGUAGE plpgsql AS 'BEGIN NEW.timestamp = NOW(); RETURN NEW; END;'
- changeSet:
id: CREATE TRIGGER update_users_set_now_to_timestamp
author: Konstantin Chvilyov
changes:
- sql:
sql: CREATE TRIGGER update_users_set_now_to_timestamp BEFORE UPDATE ON users FOR EACH ROW EXECUTE PROCEDURE set_now_to_timestamp();