How do you truncate all tables in a database using

Question

I have a test environment for a database that I want to reload with new data at the start of a testing cycle. I am not interested in rebuilding the entire database- just simply "re-setting" the data.

What is the best way to remove all the data from all the tables using TSQL? Are there system stored procedures, views, etc. that can be used? I do not want to manually create and maintain truncate table statements for each table- I would prefer it to be dynamic.

Answer 1

When dealing with deleting data from tables which have foreign key relationships - which is basically the case with any properly designed database - we can disable all the constraints, delete all the data and then re-enable constraints

-- disable all constraints
EXEC sp_MSForEachTable "ALTER TABLE ? NOCHECK CONSTRAINT all"

-- delete data in all tables
EXEC sp_MSForEachTable "DELETE FROM ?"

-- enable all constraints
exec sp_MSForEachTable "ALTER TABLE ? WITH CHECK CHECK CONSTRAINT all"

More on disabling constraints and triggers here

if some of the tables have identity columns we may want to reseed them

EXEC sp_MSForEachTable "DBCC CHECKIDENT ( '?', RESEED, 0)"

Note that the behaviour of RESEED differs between brand new table, and one which had had some data inserted previously from BOL:

DBCC CHECKIDENT ('table_name', RESEED, newReseedValue)

The current identity value is set to the newReseedValue. If no rows have been inserted to the table since it was created, the first row inserted after executing DBCC CHECKIDENT will use newReseedValue as the identity. Otherwise, the next row inserted will use newReseedValue + 1. If the value of newReseedValue is less than the maximum value in the identity column, error message 2627 will be generated on subsequent references to the table.

Thanks to Robert for pointing out the fact that disabling constraints does not allow to use truncate, the constraints would have to be dropped, and then recreated

Answer 2

The simplest way of doing this is to

1. open up SQL Management Studio
2. navigate to your database
3. Right-click and select Tasks->Generate Scripts (pic 1)
4. On the "choose Objects" screen, select the "select specific objects" option and check "tables" (pic 2)
5. on the next screen, select "advanced" and then change the "Script DROP and CREATE" option to "Script DROP and CREATE" (pic 3)
6. Choose to save script to a new editor window or a file and run as necessary.

this will give you a script that drops and recreates all your tables without the need to worry about debugging or whether you've included everything. While this performs more than just a truncate, the results are the same. Just keep in mind that your auto-incrementing primary keys will start at 0, as opposed to truncated tables which will remember the last value assigned. You can also execute this from code if you don't have access to Management studio on your PreProd or Production environments.

1.

2.

3.

Answer 3

Make an empty "template" database, take a full backup. When you need to refresh, just restore using WITH REPLACE. Fast, simple, bulletproof. And if a couple tables here or there need some base data(e.g. config information, or just basic information that makes your app run) it handles that too.

Answer 4

Run the commented out section once, populate the _TruncateList table with the tables you want truncated, then run the rest of the script. The _ScriptLog table will need to be cleaned up over time if you do this a lot.

You can modify this if you want to do all tables, just put in SELECT name INTO #TruncateList FROM sys.tables. However, you usually don't want to do them all.

Also, this will affect all foreign keys in the database, and you can modify that as well if it's too blunt-force for your application. It's not for my purposes.

/*
CREATE TABLE _ScriptLog 
(
    ID Int NOT NULL Identity(1,1)
    , DateAdded DateTime2 NOT NULL DEFAULT GetDate()
    , Script NVarChar(4000) NOT NULL
)

CREATE UNIQUE CLUSTERED INDEX IX_ScriptLog_DateAdded_ID_U_C ON _ScriptLog
(
    DateAdded
    , ID
)

CREATE TABLE _TruncateList
(
    TableName SysName PRIMARY KEY
)
*/
IF OBJECT_ID('TempDB..#DropFK') IS NOT NULL BEGIN
    DROP TABLE #DropFK
END

IF OBJECT_ID('TempDB..#TruncateList') IS NOT NULL BEGIN
    DROP TABLE #TruncateList
END

IF OBJECT_ID('TempDB..#CreateFK') IS NOT NULL BEGIN
    DROP TABLE #CreateFK
END

SELECT Scripts = 'ALTER TABLE ' + '[' + OBJECT_NAME(f.parent_object_id)+ ']'+
' DROP  CONSTRAINT ' + '[' + f.name  + ']'
INTO #DropFK
FROM .sys.foreign_keys AS f
INNER JOIN .sys.foreign_key_columns AS fc
ON f.OBJECT_ID = fc.constraint_object_id

SELECT TableName
INTO #TruncateList
FROM _TruncateList

SELECT Scripts = 'ALTER TABLE ' + const.parent_obj + '
    ADD CONSTRAINT ' + const.const_name + ' FOREIGN KEY (
            ' + const.parent_col_csv + '
            ) REFERENCES ' + const.ref_obj + '(' + const.ref_col_csv + ')
'
INTO #CreateFK
FROM (
    SELECT QUOTENAME(fk.NAME) AS [const_name]
        ,QUOTENAME(schParent.NAME) + '.' + QUOTENAME(OBJECT_name(fkc.parent_object_id)) AS [parent_obj]
        ,STUFF((
                SELECT ',' + QUOTENAME(COL_NAME(fcP.parent_object_id, fcp.parent_column_id))
                FROM sys.foreign_key_columns AS fcP
                WHERE fcp.constraint_object_id = fk.object_id
                FOR XML path('')
                ), 1, 1, '') AS [parent_col_csv]
        ,QUOTENAME(schRef.NAME) + '.' + QUOTENAME(OBJECT_NAME(fkc.referenced_object_id)) AS [ref_obj]
        ,STUFF((
                SELECT ',' + QUOTENAME(COL_NAME(fcR.referenced_object_id, fcR.referenced_column_id))
                FROM sys.foreign_key_columns AS fcR
                WHERE fcR.constraint_object_id = fk.object_id
                FOR XML path('')
                ), 1, 1, '') AS [ref_col_csv]
    FROM sys.foreign_key_columns AS fkc
    INNER JOIN sys.foreign_keys AS fk ON fk.object_id = fkc.constraint_object_id
    INNER JOIN sys.objects AS oParent ON oParent.object_id = fkc.parent_object_id
    INNER JOIN sys.schemas AS schParent ON schParent.schema_id = oParent.schema_id
    INNER JOIN sys.objects AS oRef ON oRef.object_id = fkc.referenced_object_id
    INNER JOIN sys.schemas AS schRef ON schRef.schema_id = oRef.schema_id
    GROUP BY fkc.parent_object_id
        ,fkc.referenced_object_id
        ,fk.NAME
        ,fk.object_id
        ,schParent.NAME
        ,schRef.NAME
    ) AS const
ORDER BY const.const_name

INSERT INTO _ScriptLog (Script)
SELECT Scripts
FROM #CreateFK

DECLARE @Cmd NVarChar(4000)
    , @TableName SysName

WHILE 0 < (SELECT Count(1) FROM #DropFK) BEGIN
    SELECT TOP 1 @Cmd = Scripts 
    FROM #DropFK

    EXEC (@Cmd)

    DELETE #DropFK WHERE Scripts = @Cmd
END

WHILE 0 < (SELECT Count(1) FROM #TruncateList) BEGIN
    SELECT TOP 1 @Cmd = N'TRUNCATE TABLE ' +  TableName
        , @TableName = TableName
    FROM #TruncateList

    EXEC (@Cmd)

    DELETE #TruncateList WHERE TableName = @TableName
END

WHILE 0 < (SELECT Count(1) FROM #CreateFK) BEGIN
    SELECT TOP 1 @Cmd = Scripts 
    FROM #CreateFK

    EXEC (@Cmd)

    DELETE #CreateFK WHERE Scripts = @Cmd
END

Answer 5

It is a little late but it might help someone. I created a procedure sometimes back which does the following using T-SQL:

1. Store all constraints in a Temporary table
2. Drop All Constraints
3. Truncate all tables with exception of some tables, which does not need truncation
4. Recreate all Constraints.

I have listed it on my blog here

Answer 6

If you want to keep data in a particular table (i.e. a static lookup table) while deleting/truncating data in other tables within the same db, then you need a loop with the exceptions in it. This is what I was looking for when I stumbled onto this question.

sp_MSForEachTable seems buggy to me (i.e. inconsistent behavior with IF statements) which is probably why its undocumented by MS.

declare @LastObjectID int = 0
declare @TableName nvarchar(100) = ''
set @LastObjectID = (select top 1 [object_id] from sys.tables where [object_id] > @LastObjectID order by [object_id])
while(@LastObjectID is not null)
begin
    set @TableName = (select top 1 [name] from sys.tables where [object_id] = @LastObjectID)

    if(@TableName not in ('Profiles', 'ClientDetails', 'Addresses', 'AgentDetails', 'ChainCodes', 'VendorDetails'))
    begin
        exec('truncate table [' + @TableName + ']')
    end 

    set @LastObjectID = (select top 1 [object_id] from sys.tables where [object_id] > @LastObjectID order by [object_id])
end