T-SQL: convert datatime2 to datetime for all columns of datetime2 type

Question

I have a database full of datetime2 columns than I need to migrate to the SQL 2005 database. So, I need to convert all these datetime2 (7) columns to datetime.

How can i do this?

Right now, I managed to select the table name and column name for all columns with datetime2 type as follows:

SELECT t.name, c.name, i.DATA_TYPE
FROM sys.tables AS t
JOIN sys.columns c ON t.object_id = c.object_id
JOIN information_schema.columns i ON i.TABLE_NAME = t.name AND i.COLUMN_NAME = c.name
WHERE i.data_type = 'datetime2'

I just don't know how to do the rest.

Answer 1

... Then you iterate over your results with CURSOR and dynamically run DDL, for example:

ALTER TABLE myTable ALTER COLUMN myColumn datetime [NOT] NULL

so you get something similar to this (not tested):

: ​​ :

DECLARE @SQL AS NVARCHAR(1024)
DECLARE @TBL AS NVARCHAR(255)
DECLARE @COL AS NVARCHAR(255)
DECLARE @NUL AS BIT
DECLARE CUR CURSOR FAST_FORWARD FOR
    SELECT  t.name, c.name, c.is_nullable
    FROM    sys.tables AS t
    JOIN    sys.columns c ON t.object_id = c.object_id
    JOIN    information_schema.columns i ON i.TABLE_NAME = t.name AND i.COLUMN_NAME = c.name
    WHERE   i.data_type = 'datetime2'
    ORDER BY t.name, c.name

OPEN CUR
FETCH NEXT FROM CUR INTO @TBL, @COL, @NUL
WHILE @@FETCH_STATUS = 0
BEGIN
    SELECT @SQL = 'ALTER TABLE ' + @TBL + ' ALTER COLUMN ' + @COL + ' datetime' + (CASE WHEN @NUL=1 THEN '' ELSE ' NOT' END) + ' NULL;'
    EXEC sp_executesql @SQL
    FETCH NEXT FROM CUR INTO @TBL, @COL, @NUL
END

CLOSE CUR;
DEALLOCATE CUR;

Answer 2

, , . , DDL, TSQL, TSQL, , Query . , @van ( ).

, sql:

select 'ALTER TABLE ' + table_name + ' ALTER COLUMN ' + column_name + ' datetime [NOT] NULL' 
from INFORMATION_SCHEMA.columns 
where data_type = 'datetime2(7)'.

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, SQL Mgmt Studio " " " ".

Answer 3

,

DECLARE @SQL AS NVARCHAR(1024)
DECLARE @TBL AS NVARCHAR(255)
DECLARE @COL AS NVARCHAR(255)
DECLARE @SCH AS NVARCHAR(255)
DECLARE @NUL AS BIT
DECLARE CUR CURSOR FAST_FORWARD FOR
    SELECT  t.name AS TableName, c.name ColumnName, s.name AS SchemaName, c.is_nullable
    FROM    sys.tables AS t
    JOIN    sys.columns c ON t.object_id = c.object_id
    JOIN    information_schema.columns AS i ON i.TABLE_NAME = t.name AND i.COLUMN_NAME = c.name
    JOIN    sys.schemas AS s on t.schema_id = s.schema_id
    WHERE   i.data_type = 'datetime2'    
    ORDER BY t.name, c.name

OPEN CUR
FETCH NEXT FROM CUR INTO @TBL, @COL, @SCH, @NUL
WHILE @@FETCH_STATUS = 0
BEGIN
    SELECT @SQL = 'ALTER TABLE ['+@SCH+'].[' + @TBL + '] ALTER COLUMN [' + @COL + '] datetime' + (CASE WHEN @NUL=1 THEN '' ELSE ' NOT' END) + ' NULL;'
    EXEC sp_executesql @SQL
    FETCH NEXT FROM CUR INTO @TBL, @COL,@SCH, @NUL
END

CLOSE CUR;
DEALLOCATE CUR;

Answer 4

. , datetime , , ALTER TABLE. script, , . , , .. , .

If you are in the same situation, you can use this stable and tested script, which also ensures that there is no silent truncation of the nvarchar (max) variable used to compile DDL statements:

DECLARE @sql AS nvarchar(max)=N''

--1. "ALTER TABLE [Tablename] DROP CONSTRAINT [DF__Tablename__Colname__Obfuscation]"
SELECT @sql=CAST('' AS nvarchar(MAX))+@sql 
  +N'ALTER TABLE ['+o.[name]+N'] DROP CONSTRAINT ['+co.[name]+']' 
FROM sysconstraints c 
INNER JOIN sysobjects o ON o.[id]=c.[id] 
INNER JOIN syscolumns col ON col.[id]=o.[id] AND col.colid=c.colid
INNER JOIN sysobjects co ON co.[id]=c.constid 
WHERE col.xtype=61 --datetime

EXEC sp_executesql @sql

--2. change type of all datetime columns
SELECT @sql=N''
SELECT @sql=CAST('' AS nvarchar(MAX))+@sql 
  +N'ALTER TABLE [' 
  +convert(nvarchar(max),t.name)
  +N'] ALTER COLUMN [' 
  +convert(nvarchar(max),c.name)
  +N'] datetime2 ' 
  +CASE WHEN c.is_nullable = 1 THEN N'' ELSE N'NOT' END
  +N' NULL;'+convert(nvarchar(max),char(13)+char(10))
FROM sys.tables t 
INNER JOIN sys.columns c ON t.object_id = c.object_id 
INNER JOIN sys.types st ON st.system_type_id = c.system_type_id
WHERE st.name=N'datetime'
AND t.xtype=N'U' --user tables only
ORDER BY t.[name]

EXEC sp_executesql @sql

It uses ancient syntax tables and schemas, so it works with SQL Server version 2008 (which was the first to support datetime2) until 2016.