Remove Identity Setting from all Tables which have Identity

Using SQL Server, to remove the is identity setting (auto increment) for a table, I have to drop and recreate a table.

Is there a way to disable the Idendity Setting for all tables with a simple script?

Answer

You cannot remove an IDENTITY specification once set.

I assume that you are using SQL SERVER:

You have to use dynamic SQL query to drop all Identity Columns:

DECLARE @SQL as varchar(8000)

SET @SQL = ''

select @SQL = @SQL + 'ALTER TABLE [' + [TABLE_SCHEMA] + '].[' + [TABLE_NAME] + '] DROP COLUMN [' + [COLUMN_NAME] + ']  ; '
FROM INFORMATION_SCHEMA.COLUMNS
WHERE COLUMNPROPERTY(object_id(TABLE_NAME), COLUMN_NAME, 'IsIdentity') = 1
ORDER BY  TABLE_NAME 


EXEC( @SQL)

Note: COLUMNPROPERTY is starting with SQL SERVER 2008

UPDATE1 : According to your comment the following query

• loop over Tables
• Check if table contains Identity column.
• If True, It Check if table has Relations
• If False, it check if it contains Data
• If not containing Data it drop table and recreate it without Identity.

Note: Query contains a lot of code because generating create table script

    DECLARE @strSchema as varchar(50)
    DECLARE  @strName as varchar(50)
    DECLARE @strQuery as varchar(8000)

    DECLARE csrCursor Cursor For SELECT [TABLE_SCHEMA],[TABLE_NAME] FROM INFORMATION_SCHEMA.COLUMNS
    WHERE COLUMNPROPERTY(object_id(TABLE_NAME), COLUMN_NAME, 'IsIdentity') = 1
    ORDER BY  TABLE_NAME 

    OPEN csrCursor

    FETCH NEXT FROM csrCursor INTO @strSchema,@strName

    WHILE @@FETCH_STATUS <> -1
    BEGIN

    IF NOT EXISTS(SELECT
        name, OBJECT_NAME(parent_object_id) 'Table'
    FROM 
        sys.foreign_keys
    WHERE 
        referenced_object_id = OBJECT_ID('[' + @strSchema + '].[' + @strName + ']'))

    BEGIN

    SET  @strQuery = 'IF NOT EXISTS(SELECT * FROM [' + @strSchema + '].[' + @strName + ']) 
    BEGIN
    DROP TABLE [' + @strSchema + '].[' + @strName + '];
    '

    DECLARE @table_name SYSNAME
    SELECT @table_name = @strSchema + '.' + @strName

    DECLARE 
          @object_name SYSNAME
        , @object_id INT

    SELECT 
          @object_name = '[' + s.name + '].[' + o.name + ']'
        , @object_id = o.[object_id]
    FROM sys.objects o WITH (NOWAIT)
    JOIN sys.schemas s WITH (NOWAIT) ON o.[schema_id] = s.[schema_id]
    WHERE s.name + '.' + o.name = @table_name
        AND o.[type] = 'U'
        AND o.is_ms_shipped = 0

    DECLARE @SQL NVARCHAR(MAX) = ''

    ;WITH index_column AS 
    (
        SELECT 
              ic.[object_id]
            , ic.index_id
            , ic.is_descending_key
            , ic.is_included_column
            , c.name
        FROM sys.index_columns ic WITH (NOWAIT)
        JOIN sys.columns c WITH (NOWAIT) ON ic.[object_id] = c.[object_id] AND ic.column_id = c.column_id
        WHERE ic.[object_id] = @object_id
    ),
    fk_columns AS 
    (
         SELECT 
              k.constraint_object_id
            , cname = c.name
            , rcname = rc.name
        FROM sys.foreign_key_columns k WITH (NOWAIT)
        JOIN sys.columns rc WITH (NOWAIT) ON rc.[object_id] = k.referenced_object_id AND rc.column_id = k.referenced_column_id 
        JOIN sys.columns c WITH (NOWAIT) ON c.[object_id] = k.parent_object_id AND c.column_id = k.parent_column_id
        WHERE k.parent_object_id = @object_id
    )
    SELECT @SQL = 'CREATE TABLE ' + @object_name + CHAR(13) + '(' + CHAR(13) + STUFF((
        SELECT CHAR(9) + ', [' + c.name + '] ' + 
            CASE WHEN c.is_computed = 1
                THEN 'AS ' + cc.[definition] 
                ELSE UPPER(tp.name) + 
                    CASE WHEN tp.name IN ('varchar', 'char', 'varbinary', 'binary', 'text')
                           THEN '(' + CASE WHEN c.max_length = -1 THEN 'MAX' ELSE CAST(c.max_length AS VARCHAR(5)) END + ')'
                         WHEN tp.name IN ('nvarchar', 'nchar', 'ntext')
                           THEN '(' + CASE WHEN c.max_length = -1 THEN 'MAX' ELSE CAST(c.max_length / 2 AS VARCHAR(5)) END + ')'
                         WHEN tp.name IN ('datetime2', 'time2', 'datetimeoffset') 
                           THEN '(' + CAST(c.scale AS VARCHAR(5)) + ')'
                         WHEN tp.name = 'decimal' 
                           THEN '(' + CAST(c.[precision] AS VARCHAR(5)) + ',' + CAST(c.scale AS VARCHAR(5)) + ')'
                        ELSE ''
                    END +
                    CASE WHEN c.collation_name IS NOT NULL THEN ' COLLATE ' + c.collation_name ELSE '' END +
                    CASE WHEN c.is_nullable = 1 THEN ' NULL' ELSE ' NOT NULL' END +
                    CASE WHEN dc.[definition] IS NOT NULL THEN ' DEFAULT' + dc.[definition] ELSE '' END 

            END + CHAR(13)
        FROM sys.columns c WITH (NOWAIT)
        JOIN sys.types tp WITH (NOWAIT) ON c.user_type_id = tp.user_type_id
        LEFT JOIN sys.computed_columns cc WITH (NOWAIT) ON c.[object_id] = cc.[object_id] AND c.column_id = cc.column_id
        LEFT JOIN sys.default_constraints dc WITH (NOWAIT) ON c.default_object_id != 0 AND c.[object_id] = dc.parent_object_id AND c.column_id = dc.parent_column_id
        LEFT JOIN sys.identity_columns ic WITH (NOWAIT) ON c.is_identity = 1 AND c.[object_id] = ic.[object_id] AND c.column_id = ic.column_id
        WHERE c.[object_id] = @object_id
        ORDER BY c.column_id
        FOR XML PATH(''), TYPE).value('.', 'NVARCHAR(MAX)'), 1, 2, CHAR(9) + ' ')
        + ISNULL((SELECT CHAR(9) + ', CONSTRAINT [' + k.name + '] PRIMARY KEY (' + 
                        (SELECT STUFF((
                             SELECT ', [' + c.name + '] ' + CASE WHEN ic.is_descending_key = 1 THEN 'DESC' ELSE 'ASC' END
                             FROM sys.index_columns ic WITH (NOWAIT)
                             JOIN sys.columns c WITH (NOWAIT) ON c.[object_id] = ic.[object_id] AND c.column_id = ic.column_id
                             WHERE ic.is_included_column = 0
                                 AND ic.[object_id] = k.parent_object_id 
                                 AND ic.index_id = k.unique_index_id     
                             FOR XML PATH(N''), TYPE).value('.', 'NVARCHAR(MAX)'), 1, 2, ''))
                + ')' + CHAR(13)
                FROM sys.key_constraints k WITH (NOWAIT)
                WHERE k.parent_object_id = @object_id 
                    AND k.[type] = 'PK'), '') + ')'  + CHAR(13)
        + ISNULL((SELECT (
            SELECT CHAR(13) +
                 'ALTER TABLE ' + @object_name + ' WITH' 
                + CASE WHEN fk.is_not_trusted = 1 
                    THEN ' NOCHECK' 
                    ELSE ' CHECK' 
                  END + 
                  ' ADD CONSTRAINT [' + fk.name  + '] FOREIGN KEY(' 
                  + STUFF((
                    SELECT ', [' + k.cname + ']'
                    FROM fk_columns k
                    WHERE k.constraint_object_id = fk.[object_id]
                    FOR XML PATH(''), TYPE).value('.', 'NVARCHAR(MAX)'), 1, 2, '')
                   + ')' +
                  ' REFERENCES [' + SCHEMA_NAME(ro.[schema_id]) + '].[' + ro.name + '] ('
                  + STUFF((
                    SELECT ', [' + k.rcname + ']'
                    FROM fk_columns k
                    WHERE k.constraint_object_id = fk.[object_id]
                    FOR XML PATH(''), TYPE).value('.', 'NVARCHAR(MAX)'), 1, 2, '')
                   + ')'
                + CASE 
                    WHEN fk.delete_referential_action = 1 THEN ' ON DELETE CASCADE' 
                    WHEN fk.delete_referential_action = 2 THEN ' ON DELETE SET NULL'
                    WHEN fk.delete_referential_action = 3 THEN ' ON DELETE SET DEFAULT' 
                    ELSE '' 
                  END
                + CASE 
                    WHEN fk.update_referential_action = 1 THEN ' ON UPDATE CASCADE'
                    WHEN fk.update_referential_action = 2 THEN ' ON UPDATE SET NULL'
                    WHEN fk.update_referential_action = 3 THEN ' ON UPDATE SET DEFAULT'  
                    ELSE '' 
                  END 
                + CHAR(13) + 'ALTER TABLE ' + @object_name + ' CHECK CONSTRAINT [' + fk.name  + ']' + CHAR(13)
            FROM sys.foreign_keys fk WITH (NOWAIT)
            JOIN sys.objects ro WITH (NOWAIT) ON ro.[object_id] = fk.referenced_object_id
            WHERE fk.parent_object_id = @object_id
            FOR XML PATH(N''), TYPE).value('.', 'NVARCHAR(MAX)')), '')
        + ISNULL(((SELECT
             CHAR(13) + 'CREATE' + CASE WHEN i.is_unique = 1 THEN ' UNIQUE' ELSE '' END 
                    + ' NONCLUSTERED INDEX [' + i.name + '] ON ' + @object_name + ' (' +
                    STUFF((
                    SELECT ', [' + c.name + ']' + CASE WHEN c.is_descending_key = 1 THEN ' DESC' ELSE ' ASC' END
                    FROM index_column c
                    WHERE c.is_included_column = 0
                        AND c.index_id = i.index_id
                    FOR XML PATH(''), TYPE).value('.', 'NVARCHAR(MAX)'), 1, 2, '') + ')'  
                    + ISNULL(CHAR(13) + 'INCLUDE (' + 
                        STUFF((
                        SELECT ', [' + c.name + ']'
                        FROM index_column c
                        WHERE c.is_included_column = 1
                            AND c.index_id = i.index_id
                        FOR XML PATH(''), TYPE).value('.', 'NVARCHAR(MAX)'), 1, 2, '') + ')', '')  + CHAR(13)
            FROM sys.indexes i WITH (NOWAIT)
            WHERE i.[object_id] = @object_id
                AND i.is_primary_key = 0
                AND i.[type] = 2
            FOR XML PATH(''), TYPE).value('.', 'NVARCHAR(MAX)')
        ), '')

    SET @strQuery  = @strQuery + @SQL  + '
    END'

    --PRINT(@strQuery)
    EXEC (@strQuery)

    END

    FETCH NEXT FROM csrCursor INTO @strSchema,@strName


    END 

    Close csrCursor
    DEALLOCATE csrCursor

Query is tested under SQL Server 2016 and it works fine