I would like to make the below query as dynamic SQL .
Query 1 : Table Truncation
select 'Truncate Table '+''+ name from sys.tables where name like '%RND%'
Query 2 :
select 'Insert into '+''+ name +'Select * from '+'.'+''+ name from sys.tables where name like '%RND%'
By using the following dynamic query you can truncate the required tables:
DECLARE #DynamicSQL AS VARCHAR(MAX) = '';
SELECT #DynamicSQL = #DynamicSQL + 'TRUNCATE TABLE ' + QUOTENAME(NAME) + '; '
FROM sys.tables
WHERE NAME LIKE '%RND%';
--PRINT #DynamicSQL
EXEC (#DynamicSQL)
For the second query the dynamic query is :
DECLARE #DynamicSQL1 AS VARCHAR(MAX) = '';
SELECT #DynamicSQL1 = #DynamicSQL1 + 'INSERT INTO ' + QUOTENAME(NAME) + ' SELECT * FROM ' + QUOTENAME(NAME) + '; '
FROM sys.tables
WHERE NAME LIKE '%RND%';
--PRINT #DynamicSQL1
EXEC (#DynamicSQL1)
This might be what you are looking for
All statements are collected in a table, ordered by their point of insert (id is IDENTITY). It will be - for sure - no problem for you to build your second statement in the same way...
DECLARE #cmdTbl TABLE(id INT IDENTITY,cmd NVARCHAR(MAX));
INSERT INTO #cmdTbl(cmd)
SELECT 'TRUNCATE TABLE ' + QUOTENAME(t.TABLE_CATALOG) + '.' + QUOTENAME(t.TABLE_SCHEMA) + '.' + QUOTENAME(t.TABLE_NAME) + ';'
FROM INFORMATION_SCHEMA.TABLES AS t
WHERE t.TABLE_NAME LIKE '%RND%'
--After collecting all statements I use a CURSOR to execute them one after the other.
DECLARE #cmd VARCHAR(MAX);
DECLARE cur CURSOR FOR SELECT cmd FROM #cmdTbl ORDER BY id;
OPEN cur;
FETCH NEXT FROM cur INTO #cmd;
WHILE ##FETCH_STATUS = 0
BEGIN
PRINT #cmd;
--EXEC(#cmd); --For syntax check you start without EXEC...
FETCH NEXT FROM cur INTO #cmd;
END
CLOSE cur;
DEALLOCATE cur;
Step 1:
vi truncate_count.sql
use dbname
go
---generate truncate table statements
select 'Truncate Table '+''+convert(varchar(30),o.name)+'
go' as table_name
from sysobjects o
where type = 'U'
order by table_name
go
---check the table count
select 'select count(1) from '+''+convert(varchar(30),o.name)+'
go' AS table_name
from sysobjects o
where type = 'U'
order by table_name
go
Step 2:
isql -U<USER> -S<server> -P<pwd> -w999 -D<dbname> -e -itruncate_count.sql -otruncate_count1.sql
Step 3:
Add the below lines at the starting of the file truncate_count1.sql
use dbname
go
isql -U<USER> -S<server> -P<pwd> -w999 -D<dbname> -e -itruncate_count1.sql -otruncate_count1.log
Related
I am trying to set a default value to a column(Inserted_time), but first i need to check if the column exists in the tables. If the column doesn't exist, I need to add that column and give it a default value.
I am working with Sql Server Management Studio.
So far I have written this code:
IF EXISTS ( select TABLE_NAME from INFORMATION_SCHEMA.COLUMNS where TABLE_CATALOG = 'DB_COPY' and COLUMN_NAME = 'Inserted_Time')
begin
ALTER TABLE table_name ADD CONSTRAINT [Inserted_Time_Def] SET DEFAULT (sysdatetimeoffset()) FOR [Inserted_Time]
end
else
ALTER TABLE table_name ADD COLUMN [Inserted_Time] CONSTRAINT [Inserted_Time_Def] DEFAULT (sysdatetimeoffset()) WITH VALUES
Once I retrieve the tables that has the column, I need to add that table_name to the Alter command. But I am not able to do that. Can someone please tell me how to use the table_names retrieved from select statement in the alter statement?
First, you want to put all the table names in a temporary table so you can loop through it.
After, you can use a cursor to execute a command for each table name.
In my example, I only printed the command I wanted to execute. That way you can be sure the code will do what you want first.
Example :
select TABLE_NAME As TableName INTO #TablesList from INFORMATION_SCHEMA.COLUMNS where TABLE_CATALOG = 'DB_COPY' and COLUMN_NAME = 'Inserted_Time'
DECLARE #TablesCursor as CURSOR;
DECLARE #TableName as NVARCHAR(max);
DECLARE #CommandToExecute as NVARCHAR(max);
SET #TablesCursor = CURSOR FOR SELECT TableName FROM #TablesList;
OPEN #TablesCursor;
FETCH NEXT FROM #TablesCursor INTO #TableName;
WHILE ##FETCH_STATUS = 0
BEGIN
SET #CommandToExecute = 'ALTER TABLE ' + #TableName + ' WHAT YOU WANNA DO '
PRINT #CommandToExecute
--EXEC(#CommandToExecute)
FETCH NEXT FROM #TablesCursor INTO #TableName;
END
CLOSE #TablesCursor;
DEALLOCATE #TablesCursor;
Assuming that every table is in a different schema, then you could do something like this:
DECLARE #SQL nvarchar(MAX);
SET #SQL = STUFF((SELECT NCHAR(13) + NCHAR(10) +
CASE WHEN EXISTS (SELECT 1
FROM INFORMATION_SCHEMA.COLUMNS C
WHERE T.TABLE_SCHEMA = C.TABLE_SCHEMA
AND T.TABLE_NAME = C.TABLE_SCHEMA
AND C.COLUMN_NAME = N'Inserted_Time') THEN N'ALTER TABLE ' + QUOTENAME(T.TABLE_SCHEMA) + N'.' + QUOTENAME(T.TABLE_NAME) + N' ADD CONSTRAINT [Inserted_Time_Def] DEFAULT (sysdatetimeoffset()) FOR [Inserted_Time];'
ELSE N'ALTER TABLE ' + QUOTENAME(T.TABLE_SCHEMA) + N'.' + QUOTENAME(T.TABLE_NAME) + N' ADD COLUMN [Inserted_Time] CONSTRAINT [Inserted_Time_Def] DEFAULT (sysdatetimeoffset());'
END
FROM INFORMATION_SCHEMA.TABLES T
WHERE T.TABLE_CATALOG = N'DB_COPY'
FOR XML PATH(N''),TYPE).value('.','nvarchar(MAX)'),1,2,N'');
PRINT #SQL; --Your best friend. If more than 4,000 characters, use SELECT
EXECUTE sp_executesql #SQL;
This will very likely hugely out perform a CURSOR solution if you have a large number of schemas.
I want to delete the ABCDEF column from all tables of my database. I am trying this code:
declare #SQL nvarchar(max)
SELECT
#SQL = STUFF((SELECT ' DROP column ' + quotename(TABLE_SCHEMA) + '.' + quotename(table_NAME ) +'.ABCDEF;'
FROM
information_schema.columns
FOR XML PATH('')),1,2,'')
PRINT #SQL
EXECUTE (#SQL)
But I am getting an error
incorrect syntax near column
How to do this?
You can use an undocumented feature of SQL Server sys.sp_msforeachtable. The below script will basically iterate for all the tables in database and alter them if required.
select '[dbo].['+tab.name+']' name into #table from
sys.tables tab join sys.columns col on tab.object_id = col.object_id and col.name = 'ABCDEF'
exec sys.sp_msforeachtable 'if exists (select 1 from #table where name = ''?'')
alter table ? drop column [ABCDEF]'
That's not the right way to drop a column from a table. It should be
ALTER TABLE table_name DROP COLUMN column_name
Build your dynamic query something like this:
DECLARE #sql NVARCHAR(max)=''
SELECT #SQL += 'Alter table ' + Quotename(table_catalog)
+ '.' + Quotename(table_schema) + '.'
+ Quotename(TABLE_NAME) + ' DROP column '
+ Quotename(column_name) + ';'
FROM information_schema.columns where COLUMN_NAME = 'abcd' -- Here alone mention
--the Column to be removed
EXEC Sp_executesql #sql
While dropping the columns from multiple tables, I faced following default constraints error.
The object 'DF_TableName_ColumnName' is dependent on column 'ColumnName'.
To resolve this, I have to drop all those constraints first, by using following query
DECLARE #sql NVARCHAR(max)=''
SELECT #SQL += 'Alter table ' + Quotename(tbl.name) + ' DROP constraint ' + Quotename(cons.name) + ';'
FROM SYS.DEFAULT_CONSTRAINTS cons
JOIN SYS.COLUMNS col ON col.default_object_id = cons.object_id
JOIN SYS.TABLES tbl ON tbl.object_id = col.object_id
WHERE col.[name] IN ('Column1','Column2')
--PRINT #sql
EXEC Sp_executesql #sql
After that, I dropped all those columns by using the answer above.
DECLARE #sql NVARCHAR(max)=''
SELECT #SQL += 'Alter table ' + Quotename(table_catalog)+ '.' + Quotename(table_schema) + '.'+ Quotename(TABLE_NAME)
+ ' DROP column ' + Quotename(column_name) + ';'
FROM information_schema.columns where COLUMN_NAME IN ('Column1','Column2')
--PRINT #sql
EXEC Sp_executesql #sql
I posted here in case someone find the same issue.
Happy Coding!
Using SQL Server 2008, I'd like to create a UDF that gives me the create date of an object. This is the code:
create function dbo.GetObjCreateDate(#objName sysname) returns datetime as
begin
declare #result datetime
select #result = create_date from sys.objects where name = #objname
return #result
end
go
I'd like to put this UDF in the master database or some other shared database so that it is accessible from anywhere, except that if I do that then the sys.objects reference pulls from the master database instead of the database that I'm initiating my query from. I know you can do this as the information_schema views sit in master and just wrap calls to local instances of sys.objects, so I'm hoping there's a simple way to do that with my UDF as well.
Try this:
CREATE FUNCTION dbo.GetObjCreateDate(#objName sysname, #dbName sysname)
RETURNS datetime AS
BEGIN
DECLARE #createDate datetime;
DECLARE #params nvarchar(50);
DECLARE #sql nvarchar(500);
SET #params = '#createDate datetime OUTPUT';
SELECT #sql = 'SELECT #createDate = create_date FROM ' + #dbName + '.sys.objects WHERE name = ''' + #objname + '''';
EXEC sp_executesql #sql, #params, #createDate = #createDate OUTPUT;
RETURN #createDate
END
;
Why not do this instead?
Create a stored procedure that creates a view in the master database containing all of the information in sys.objects from each database on the server.
Create a DDL Trigger that gets fired whenever a CREATE, ALTER or DROP statement is executed for a database. The trigger would then execute the stored procedure in step #1. This allows the view to be automatically updated.
(Optional) Create a user defined function that queries the view for the creation date of a given object.
Stored Procedure DDL:
USE [master];
GO
CREATE PROCEDURE dbo.BuildAllServerObjectsView
AS
SET NOCOUNT ON;
IF OBJECT_ID('master.dbo.AllServerObjects') IS NOT NULL
EXEC master..sp_SQLExec 'DROP VIEW dbo.AllServerObjects;';
IF OBJECT_ID('tempdb..Databases') IS NOT NULL
DROP TABLE #Databases;
DECLARE #CreateView varchar(8000);
SET #CreateView = 'CREATE VIEW dbo.AllServerObjects AS' + CHAR(13)+CHAR(10) + CHAR(13)+CHAR(10);
SELECT name COLLATE SQL_Latin1_General_CP1_CI_AS AS 'name'
INTO #Databases
FROM sys.databases
ORDER BY name;
DECLARE #DatabaseName nvarchar(100);
WHILE (SELECT COUNT(*) FROM #Databases) > 0
BEGIN
SET #DatabaseName = (SELECT TOP 1 name FROM #Databases ORDER BY name);
SET #CreateView +='SELECT N'+QUOTENAME(#DatabaseName, '''')+' AS ''database_name''' + CHAR(13)+CHAR(10)
+ ' ,name COLLATE SQL_Latin1_General_CP1_CI_AS AS ''object_name''' + CHAR(13)+CHAR(10)
+ ' ,object_id' + CHAR(13)+CHAR(10)
+ ' ,principal_id' + CHAR(13)+CHAR(10)
+ ' ,schema_id' + CHAR(13)+CHAR(10)
+ ' ,parent_object_id' + CHAR(13)+CHAR(10)
+ ' ,type' + CHAR(13)+CHAR(10)
+ ' ,type_desc' + CHAR(13)+CHAR(10)
+ ' ,create_date' + CHAR(13)+CHAR(10)
+ ' ,modify_date' + CHAR(13)+CHAR(10)
+ ' ,is_ms_shipped' + CHAR(13)+CHAR(10)
+ ' ,is_published' + CHAR(13)+CHAR(10)
+ ' ,is_schema_published' + CHAR(13)+CHAR(10)
+ ' FROM ' + QUOTENAME(#DatabaseName) + '.sys.objects';
IF (SELECT COUNT(*) FROM #Databases) > 1
SET #CreateView += CHAR(13)+CHAR(10) + CHAR(13)+CHAR(10) + ' UNION' + CHAR(13)+CHAR(10);
ELSE
SET #CreateView += ';';
DELETE #Databases
WHERE name = #DatabaseName;
END;
--PRINT #CreateView --<== Uncomment this to see the DDL for the view.
EXEC master..sp_SQLExec #CreateView;
IF OBJECT_ID('tempdb..Databases') IS NOT NULL
DROP TABLE #Databases;
GO
Function DDL:
USE [master];
GO
CREATE FUNCTION dbo.GetObjCreateDate(#DatabaseName sysname, #objName sysname) RETURNS DATETIME AS
BEGIN
DECLARE #result datetime;
SELECT #result = create_date
FROM master.dbo.AllServerObjects
WHERE [database_name] = #DatabaseName
AND [object_name] = #objname;
RETURN #result;
END
GO
Sample Usage:
SELECT master.dbo.GetObjCreateDate('MyDatabase', 'SomeObject') AS 'Created';
SELECT master.dbo.GetObjCreateDate(DB_NAME(), 'spt_monitor') AS 'Created';
Does it have to be a function? If you just want it accessible everywhere, a trick is to put your code in a varchar and sp_executesql it:
create procedure dbo.GetObjCreateDate(#objName sysname)
as
declare #sql nvarchar(max)
select #sql = 'select create_date from sys.objects where name = ''' + #objname + ''''
EXEC sp_executesql #sql
go
There seems to be an undocumented stored procedure that allows you to create your own system objects: sp_ms_marksystemobject
You can read more on http://www.mssqltips.com/tip.asp?tip=1612
Have a look at How to Write Your Own System Functions. I believe that it may help you
I have tables like lg-010-a..., lg-010-ac..., and so on, I have abc database,
I have a command window:
drop table from abc where Table_Name like 'lg-010-%'
Will this drop all the tables starting with lg-010-?
Try something like this:
declare #sql varchar(max)
declare #tablenames varchar(max)
select #tablenames = coalesce(#tablenames + ', ','') + Table_Name from INFORMATION_SCHEMA.TABLES
where Table_Name like ('lg-010-%')
set #sql = 'drop table ' + #tablenames
exec (#sql)
This queries the INFORMATION_SCHEMA.TABLES table to retrieve table names that match your criteria, then concatenates them together into a comma delimited string.
This string is than added to a 'Drop table ' statement and executed.
Drop table can take multiple comma delimited table names.
(I had originally had this query sys.tables but some research revealed that while they are currently equivalent, the Information_Schema method is quaranteed to work in future versions)
Unfortunately you can't do it like that. One way is:
SELECT 'DROP TABLE ' + name FROM sysobjects WHERE name LIKE '%lg-010-a%' AND [type] IN ('P')
This will just print out the DROP TABLE statement for each table - you can then copy and paste this output and run it. You can just put an EXECUTE in the loop instead of the PRINT, but I've done it this way so you can see what's going on/check the output first.
I had an issue where the accepted answer was not doing anything. I discovered that I had to add the prefix name of the database to the code to get it to work. If your tables are not dbo.tablename try this.
declare #sql varchar(max)
declare #tablenames varchar(max)
SELECT
#tablenames = COALESCE(#tablenames + ', ','') + 'YourDatabaseName.' + Table_Name
FROM
INFORMATION_SCHEMA.TABLES
WHERE TABLE_TYPE = 'BASE TABLE'
AND TABLE_NAME LIKE 'AP2%'
AND (RIGHT(TABLE_NAME, 6) < 201708)
SET #sql = 'drop table ' + #tablenames
EXEC (#sql)
GO
Unfortunately you can't do it like that.
One way is:
DECLARE #TableName NVARCHAR(128)
SELECT TOP 1 #TableName = TABLE_NAME
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_NAME LIKE 'lg-010-%'
ORDER BY TABLE_NAME ASC
WHILE (##ROWCOUNT > 0)
BEGIN
PRINT 'DROP TABLE [' + #TableName + ']'
SELECT TOP 1 #TableName = TABLE_NAME
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_NAME LIKE 'lg-010-%'
AND TABLE_NAME > #TableName
ORDER BY TABLE_NAME ASC
END
This will just print out the DROP TABLE statement for each table - you can then copy and paste this output and run it. You can just put an EXECUTE in the loop instead of the PRINT, but I've done it this way so you can see what's going on/check the output first.
CREATE PROCEDURE dbo.drop_MsSqlTables1 #createDate smalldatetime
AS
declare #flag int =1
declare #tname varchar(50)
declare #sql varchar(max)
select row_number() over (order by name) as num, '[dbo].[' + name +']' as table_name into #temp from sys.tables where name like ('EmpInfo_%') and create_date<#createDate
declare #count int = (select count(*) from #temp)
select * from #temp
while #flag <= #count
begin
set #tname = (select table_name from #temp where num = #flag)
set #sql = 'drop table ' + #tname
exec (#sql)
set #flag = #flag+1
end
How do I select all the columns in a table that only contain NULL values for all the rows? I'm using MS SQL Server 2005. I'm trying to find out which columns are not used in the table so I can delete them.
Here is the sql 2005 or later version: Replace ADDR_Address with your tablename.
declare #col varchar(255), #cmd varchar(max)
DECLARE getinfo cursor for
SELECT c.name FROM sys.tables t JOIN sys.columns c ON t.Object_ID = c.Object_ID
WHERE t.Name = 'ADDR_Address'
OPEN getinfo
FETCH NEXT FROM getinfo into #col
WHILE ##FETCH_STATUS = 0
BEGIN
SELECT #cmd = 'IF NOT EXISTS (SELECT top 1 * FROM ADDR_Address WHERE [' + #col + '] IS NOT NULL) BEGIN print ''' + #col + ''' end'
EXEC(#cmd)
FETCH NEXT FROM getinfo into #col
END
CLOSE getinfo
DEALLOCATE getinfo
SELECT cols
FROM table
WHERE cols IS NULL
This should give you a list of all columns in the table "Person" that has only NULL-values. You will get the results as multiple result-sets, which are either empty or contains the name of a single column. You need to replace "Person" in two places to use it with another table.
DECLARE crs CURSOR LOCAL FAST_FORWARD FOR SELECT name FROM syscolumns WHERE id=OBJECT_ID('Person')
OPEN crs
DECLARE #name sysname
FETCH NEXT FROM crs INTO #name
WHILE ##FETCH_STATUS = 0
BEGIN
EXEC('SELECT ''' + #name + ''' WHERE NOT EXISTS (SELECT * FROM Person WHERE ' + #name + ' IS NOT NULL)')
FETCH NEXT FROM crs INTO #name
END
CLOSE crs
DEALLOCATE crs
Or did you want to just see if a column only has NULL values (and, thus, is probably unused)?
Further clarification of the question might help.
EDIT:
Ok.. here's some really rough code to get you going...
SET NOCOUNT ON
DECLARE #TableName Varchar(100)
SET #TableName='YourTableName'
CREATE TABLE #NullColumns (ColumnName Varchar(100), OnlyNulls BIT)
INSERT INTO #NullColumns (ColumnName, OnlyNulls) SELECT c.name, 0 FROM syscolumns c INNER JOIN sysobjects o ON c.id = o.id AND o.name = #TableName AND o.xtype = 'U'
DECLARE #DynamicSQL AS Nvarchar(2000)
DECLARE #ColumnName Varchar(100)
DECLARE #RC INT
SELECT TOP 1 #ColumnName = ColumnName FROM #NullColumns WHERE OnlyNulls=0
WHILE ##ROWCOUNT > 0
BEGIN
SET #RC=0
SET #DynamicSQL = 'SELECT TOP 1 1 As HasNonNulls FROM ' + #TableName + ' (nolock) WHERE ''' + #ColumnName + ''' IS NOT NULL'
EXEC sp_executesql #DynamicSQL
set #RC=##rowcount
IF #RC=1
BEGIN
SET #DynamicSQL = 'UPDATE #NullColumns SET OnlyNulls=1 WHERE ColumnName=''' + #ColumnName + ''''
EXEC sp_executesql #DynamicSQL
END
ELSE
BEGIN
SET #DynamicSQL = 'DELETE FROM #NullColumns WHERE ColumnName=''' + #ColumnName+ ''''
EXEC sp_executesql #DynamicSQL
END
SELECT TOP 1 #ColumnName = ColumnName FROM #NullColumns WHERE OnlyNulls=0
END
SELECT * FROM #NullColumns
DROP TABLE #NullColumns
SET NOCOUNT OFF
Yes, there are easier ways, but I have a meeting to go to right now. Good luck!
Here is an updated version of Bryan's query for 2008 and later. It uses INFORMATION_SCHEMA.COLUMNS, adds variables for the table schema and table name. The column data type was added to the output. Including the column data type helps when looking for a column of a particular data type. I didn't added the column widths or anything.
For output the RAISERROR ... WITH NOWAIT is used so text will display immediately instead of all at once (for the most part) at the end like PRINT does.
SET NOCOUNT ON;
DECLARE
#ColumnName sysname
,#DataType nvarchar(128)
,#cmd nvarchar(max)
,#TableSchema nvarchar(128) = 'dbo'
,#TableName sysname = 'TableName';
DECLARE getinfo CURSOR FOR
SELECT
c.COLUMN_NAME
,c.DATA_TYPE
FROM
INFORMATION_SCHEMA.COLUMNS AS c
WHERE
c.TABLE_SCHEMA = #TableSchema
AND c.TABLE_NAME = #TableName;
OPEN getinfo;
FETCH NEXT FROM getinfo INTO #ColumnName, #DataType;
WHILE ##FETCH_STATUS = 0
BEGIN
SET #cmd = N'IF NOT EXISTS (SELECT * FROM ' + #TableSchema + N'.' + #TableName + N' WHERE [' + #ColumnName + N'] IS NOT NULL) RAISERROR(''' + #ColumnName + N' (' + #DataType + N')'', 0, 0) WITH NOWAIT;';
EXECUTE (#cmd);
FETCH NEXT FROM getinfo INTO #ColumnName, #DataType;
END;
CLOSE getinfo;
DEALLOCATE getinfo;
You can do:
select
count(<columnName>)
from
<tableName>
If the count returns 0 that means that all rows in that column all NULL (or there is no rows at all in the table)
can be changed to
select
case(count(<columnName>)) when 0 then 'Nulls Only' else 'Some Values' end
from
<tableName>
If you want to automate it you can use system tables to iterate the column names in the table you are interested in
If you need to list all rows where all the column values are NULL, then i'd use the COLLATE function. This takes a list of values and returns the first non-null value. If you add all the column names to the list, then use IS NULL, you should get all the rows containing only nulls.
SELECT * FROM MyTable WHERE COLLATE(Col1, Col2, Col3, Col4......) IS NULL
You shouldn't really have any tables with ALL the columns null, as this means you don't have a primary key (not allowed to be null). Not having a primary key is something to be avoided; this breaks the first normal form.
Try this -
DECLARE #table VARCHAR(100) = 'dbo.table'
DECLARE #sql NVARCHAR(MAX) = ''
SELECT #sql = #sql + 'IF NOT EXISTS(SELECT 1 FROM ' + #table + ' WHERE ' + c.name + ' IS NOT NULL) PRINT ''' + c.name + ''''
FROM sys.objects o
JOIN sys.columns c ON o.[object_id] = c.[object_id]
WHERE o.[type] = 'U'
AND o.[object_id] = OBJECT_ID(#table)
AND c.is_nullable = 1
EXEC(#sql)
Not actually sure about 2005, but 2008 ate it:
USE [DATABASE_NAME] -- !
GO
DECLARE #SQL NVARCHAR(MAX)
DECLARE #TableName VARCHAR(255)
SET #TableName = 'TABLE_NAME' -- !
SELECT #SQL =
(
SELECT
CHAR(10)
+'DELETE FROM ['+t1.TABLE_CATALOG+'].['+t1.TABLE_SCHEMA+'].['+t1.TABLE_NAME+'] WHERE '
+(
SELECT
CASE t2.ORDINAL_POSITION
WHEN (SELECT MIN(t3.ORDINAL_POSITION) FROM INFORMATION_SCHEMA.COLUMNS t3 WHERE t3.TABLE_NAME=t2.TABLE_NAME) THEN ''
ELSE 'AND '
END
+'['+COLUMN_NAME+'] IS NULL' AS 'data()'
FROM INFORMATION_SCHEMA.COLUMNS t2 WHERE t2.TABLE_NAME=t1.TABLE_NAME FOR XML PATH('')
) AS 'data()'
FROM INFORMATION_SCHEMA.TABLES t1 WHERE t1.TABLE_NAME = #TableName FOR XML PATH('')
)
SELECT #SQL -- EXEC(#SQL)
Here I have created a script for any kind of SQL table. please copy this stored procedure and create this on your Environment and run this stored procedure with your Table.
exec [dbo].[SP_RemoveNullValues] 'Your_Table_Name'
stored procedure
GO
/****** Object: StoredProcedure [dbo].[SP_RemoveNullValues] Script Date: 09/09/2019 11:26:53 AM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- akila liyanaarachchi
Create procedure [dbo].[SP_RemoveNullValues](#PTableName Varchar(50) ) as
begin
DECLARE Cussor CURSOR FOR
SELECT COLUMN_NAME,TABLE_NAME,DATA_TYPE
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = #PTableName
OPEN Cussor;
Declare #ColumnName Varchar(50)
Declare #TableName Varchar(50)
Declare #DataType Varchar(50)
Declare #Flage int
FETCH NEXT FROM Cussor INTO #ColumnName,#TableName,#DataType
WHILE ##FETCH_STATUS = 0
BEGIN
set #Flage=0
If(#DataType in('bigint','numeric','bit','smallint','decimal','smallmoney','int','tinyint','money','float','real'))
begin
set #Flage=1
end
If(#DataType in('date','atetimeoffset','datetime2','smalldatetime','datetime','time'))
begin
set #Flage=2
end
If(#DataType in('char','varchar','text','nchar','nvarchar','ntext'))
begin
set #Flage=3
end
If(#DataType in('binary','varbinary'))
begin
set #Flage=4
end
DECLARE #SQL VARCHAR(MAX)
if (#Flage in(1,4))
begin
SET #SQL =' update ['+#TableName+'] set ['+#ColumnName+']=0 where ['+#ColumnName+'] is null'
end
if (#Flage =3)
begin
SET #SQL =' update ['+#TableName+'] set ['+#ColumnName+'] = '''' where ['+#ColumnName+'] is null '
end
if (#Flage =2)
begin
SET #SQL =' update ['+#TableName+'] set ['+#ColumnName+'] ='+'''1901-01-01 00:00:00.000'''+' where ['+#ColumnName+'] is null '
end
EXEC(#SQL)
FETCH NEXT FROM Cussor INTO #ColumnName,#TableName,#DataType
END
CLOSE Cussor
DEALLOCATE Cussor
END
You'll have to loop over the set of columns and check each one. You should be able to get a list of all columns with a DESCRIBE table command.
Pseudo-code:
foreach $column ($cols) {
query("SELECT count(*) FROM table WHERE $column IS NOT NULL")
if($result is zero) {
# $column contains only null values"
push #onlyNullColumns, $column;
} else {
# $column contains non-null values
}
}
return #onlyNullColumns;
I know this seems a little counterintuitive but SQL does not provide a native method of selecting columns, only rows.
I would also recommend to search for fields which all have the same value, not just NULL.
That is, for each column in each table do the query:
SELECT COUNT(DISTINCT field) FROM tableName
and concentrate on those which return 1 as a result.
SELECT t.column_name
FROM user_tab_columns t
WHERE t.nullable = 'Y' AND t.table_name = 'table name here' AND t.num_distinct = 0;
An updated version of 'user2466387' version, with an additional small test which can improve performance, because it's useless to test non nullable columns:
AND IS_NULLABLE = 'YES'
The full code:
SET NOCOUNT ON;
DECLARE
#ColumnName sysname
,#DataType nvarchar(128)
,#cmd nvarchar(max)
,#TableSchema nvarchar(128) = 'dbo'
,#TableName sysname = 'TableName';
DECLARE getinfo CURSOR FOR
SELECT
c.COLUMN_NAME
,c.DATA_TYPE
FROM
INFORMATION_SCHEMA.COLUMNS AS c
WHERE
c.TABLE_SCHEMA = #TableSchema
AND c.TABLE_NAME = #TableName
AND IS_NULLABLE = 'YES';
OPEN getinfo;
FETCH NEXT FROM getinfo INTO #ColumnName, #DataType;
WHILE ##FETCH_STATUS = 0
BEGIN
SET #cmd = N'IF NOT EXISTS (SELECT * FROM ' + #TableSchema + N'.' + #TableName + N' WHERE [' + #ColumnName + N'] IS NOT NULL) RAISERROR(''' + #ColumnName + N' (' + #DataType + N')'', 0, 0) WITH NOWAIT;';
EXECUTE (#cmd);
FETCH NEXT FROM getinfo INTO #ColumnName, #DataType;
END;
CLOSE getinfo;
DEALLOCATE getinfo;
You might need to clarify a bit. What are you really trying to accomplish? If you really want to find out the column names that only contain null values, then you will have to loop through the scheama and do a dynamic query based on that.
I don't know which DBMS you are using, so I'll put some pseudo-code here.
for each col
begin
#cmd = 'if not exists (select * from tablename where ' + col + ' is not null begin print ' + col + ' end'
exec(#cmd)
end