How to delete all rows from all tables in a SQL Server database?

Question

How to delete all rows from all tables in a SQL Server database?

Answer 1

--Load tables to delete from
SELECT 
DISTINCT
' Delete top 1000000 from ..' + c.TABLE_NAME + ' WHERE ' AS query,c.TABLE_NAME AS TableName, IsDeleted=0, '' AS [Source]--,t.TABLE_TYPE, c.*
            INTO dbo.AllTablesToDeleteFrom
            FROM INFORMATION_SCHEMA.TABLES AS t
            INNER JOIN information_schema.columns c ON c.TABLE_NAME = t.TABLE_NAME 
    WHERE c.COLUMN_NAME = ''
           AND c.TABLE_SCHEMA = 'dbo'
           AND c.TABLE_CATALOG = ''
           AND t.TABLE_TYPE='Base table'
           --AND t.TABLE_NAME LIKE ''

            DECLARE @TableSelect NVARCHAR(1000)= '';
            DECLARE @Table NVARCHAR(1000)= '';
            DECLARE @IsDeleted INT= 0;
            DECLARE @NumRows INT = 1000000;
            DECLARE @Source NVARCHAR(50)='';


            WHILE ( @IsDeleted = 0 )
                BEGIN
                --This grabs one table at a time to be deleted from. @TableSelect has the sql to execute. it is important to order by IsDeleted ASC
                --because it will pull tables to delete from by those that have a 0=IsDeleted first. Once the loop grabs a table with IsDeleted=1 then this will pop out of loop

                    SELECT TOP 1
                            @TableSelect = query,
                            @IsDeleted = IsDeleted,
                            @Table = TableName,
                            @Source=[a].[Source]
                    FROM    dbo.AllTablesToDeleteFrom a
                    WHERE a.[Source]='SomeDescriptorHere'--use only if needed
                    ORDER BY a.IsDeleted ASC;--this is required because only those records returned with IsDeleted=0 will run through loop

                    --SELECT  @Table; can add this in to  monitor what table is being deleted from

                    WHILE ( @NumRows = 1000000 )--only delete a million rows at a time?

                    BEGIN 
                    EXEC sp_executesql @TableSelect;
                    SET @NumRows = @@ROWCOUNT;
                    --IF @NumRows = 1000000 --can do something here if needed
                    --One wants this loop to continue as long as a million rows is deleted. Once < 1 million rows is deleted it pops out of loop
                    --and grabs next table to delete
                    --    BEGIN
                    --SELECT  @NumRows;--can add this in to see current number of deleted records for table
                            INSERT  INTO dbo.DeleteFromAllTables
                                    ( tableName,
                                      query,
                                      cnt,
                                      [Source]
                                    )
                            SELECT  @Table,
                                    @TableSelect,
                                    @NumRows,
                                    @Source;
                     --   END; 
                END; 



SET @NumRows = 1000000;

UPDATE  a
SET     a.IsDeleted = 1
FROM    dbo.AllTablesToDeleteFrom a
WHERE   a.TableName = @Table;
--flag this as deleted so you can move on to the next table to delete from

END;