--Remove all data from a database

SET NOCOUNT ON
--Tables to ignore
DECLARE @IgnoreTables
TABLE (TableName varchar(512))
INSERT INTO @IgnoreTables (TableName) VALUES ('sysdiagrams')
DECLARE @AllRelationshi
TABLE (ForeignKey varchar(512)
,TableName varchar(512)
,ColumnName varchar(512)
,ReferenceTableName varchar(512)
,ReferenceColumnName varchar(512)
,DeleteRule varchar(512))
INSERT INTO @AllRelationships
SELECT f.name AS ForeignKey,
OBJECT_NAME(f.parent_object_id) AS TableName,
COL_NAME(fc.parent_object_id,
fc.parent_column_id) AS ColumnName,
OBJECT_NAME (f.referenced_object_id) AS ReferenceTableName,
COL_NAME(fc.referenced_object_id,
fc.referenced_column_id) AS ReferenceColumnName,
delete_referential_action_desc as DeleteRule
FROM sys.foreign_keys AS f
INNER JOIN sys.foreign_key_columns AS fc
ON f.OBJECT_ID = fc.constraint_object_id

DECLARE @TableOwner varchar(512)
DECLARE @TableName varchar(512)
DECLARE @ForeignKey varchar(512)
DECLARE @ColumnName varchar(512)
DECLARE @ReferenceTableName varchar(512)
DECLARE @ReferenceColumnName varchar(512)
DECLARE @DeleteRule varchar(512)

PRINT('Loop through all tables and switch all constraints to have a delete rule of CASCADE')
DECLARE DataBaseTables0
CURSOR FOR
SELECT SCHEMA_NAME(t.schema_id) AS schema_name, t.name AS table_name
FROM sys.tables AS t;

OPEN DataBaseTables0;

FETCH NEXT FROM DataBaseTables0
INTO @TableOwner,@TableName;

WHILE @@FETCH_STATUS = 0
BEGIN
IF (NOT EXISTS(SELECT TOP 1 1 FROM @IgnoreTables WHERE TableName = @TableName))
BEGIN
PRINT '['+@TableOwner+'].[' + @TableName + ']';

DECLARE DataBaseTableRelationships CURSOR FOR
SELECT ForeignKey, ColumnName, ReferenceTableName, ReferenceColumnName
FROM @AllRelationships
WHERE TableName = @TableName

OPEN DataBaseTableRelationships;
FETCH NEXT FROM DataBaseTableRelationships INTO @ForeignKey, @ColumnName, @ReferenceTableName, @ReferenceColumnName;

IF @@FETCH_STATUS <> 0
PRINT '=====> No Relationships' ;

WHILE @@FETCH_STATUS = 0
BEGIN
PRINT '=====> switching delete rule on ' + @ForeignKey + ' to CASCADE';
BEGIN TRANSACTION
BEGIN TRY
EXEC('

ALTER TABLE ['+@TableOwner+'].[' + @TableName + ']
DROP CONSTRAINT '+@ForeignKey+';

ALTER TABLE ['+@TableOwner+'].[' + @TableName + '] ADD CONSTRAINT
'+@ForeignKey+' FOREIGN KEY
(
'+@ColumnName+'
) REFERENCES '+@ReferenceTableName+'
(
'+@ReferenceColumnName+'
) ON DELETE CASCADE;
');
COMMIT TRANSACTION
END TRY
BEGIN CATCH
PRINT '=====> can''t switch ' + @ForeignKey + ' to CASCADE, - ' +
CAST(ERROR_NUMBER() AS VARCHAR) + ' - ' + ERROR_MESSAGE();
ROLLBACK TRANSACTION
END CATCH;

FETCH NEXT FROM DataBaseTableRelationships INTO @ForeignKey, @ColumnName, @ReferenceTableName, @ReferenceColumnName;
END;

CLOSE DataBaseTableRelationships;
DEALLOCATE DataBaseTableRelationships;

END
PRINT '';
PRINT '';

FETCH NEXT FROM DataBaseTables0
INTO @TableOwner,@TableName;
END
CLOSE DataBaseTables0;
DEALLOCATE DataBaseTables0;

PRINT('Loop though each table and DELETE All data from the table')

DECLARE DataBaseTables1 CURSOR FOR
SELECT SCHEMA_NAME(t.schema_id) AS schema_name, t.name AS table_name
FROM sys.tables AS t;

OPEN DataBaseTables1;

FETCH NEXT FROM DataBaseTables1
INTO @TableOwner,@TableName;

WHILE @@FETCH_STATUS = 0
BEGIN
IF (NOT EXISTS(SELECT TOP 1 1 FROM @IgnoreTables WHERE TableName = @TableName))
BEGIN
PRINT '['+@TableOwner+'].[' + @TableName + ']';
PRINT '=====> deleting data from ['+@TableOwner+'].[' + @TableName + ']';
BEGIN TRY
EXEC('
DELETE FROM ['+@TableOwner+'].[' + @TableName + ']
DBCC CHECKIDENT ([' + @TableName + '], RESEED, 0)
');
END TRY
BEGIN CATCH
PRINT '=====> can''t FROM ['+@TableOwner+'].[' + @TableName + '], - ' +
CAST(ERROR_NUMBER() AS VARCHAR) + ' - ' + ERROR_MESSAGE();
END CATCH;
END

PRINT '';
PRINT '';

FETCH NEXT FROM DataBaseTables1
INTO @TableOwner,@TableName;
END
CLOSE DataBaseTables1;
DEALLOCATE DataBaseTables1;

PRINT('Loop through all tables and switch all constraints to have a delete rule they had at the beggining of the task')

DECLARE DataBaseTables2 CURSOR FOR
SELECT SCHEMA_NAME(t.schema_id) AS schema_name, t.name AS table_name
FROM sys.tables AS t;
OPEN DataBaseTables2;

FETCH NEXT FROM DataBaseTables2
INTO @TableOwner,@TableName;

WHILE @@FETCH_STATUS = 0
BEGIN

IF (NOT EXISTS(SELECT TOP 1 1 FROM @IgnoreTables WHERE TableName = @TableName))
BEGIN
PRINT '['+@TableOwner+'].[' + @TableName + ']';

DECLARE DataBaseTableRelationships CURSOR FOR
SELECT ForeignKey, ColumnName, ReferenceTableName, ReferenceColumnName, DeleteRule
FROM @AllRelationships
WHERE TableName = @TableName

OPEN DataBaseTableRelationships;
FETCH NEXT FROM DataBaseTableRelationships INTO @ForeignKey, @ColumnName, @ReferenceTableName, @ReferenceColumnName, @DeleteRule;

IF @@FETCH_STATUS <> 0
PRINT '=====> No Relationships' ;

WHILE @@FETCH_STATUS = 0
BEGIN
DECLARE @switchBackTo varchar(50) =
CASE
WHEN @DeleteRule = 'NO_ACTION' THEN 'NO ACTION'
WHEN @DeleteRule = 'CASCADE' THEN 'CASCADE'
WHEN @DeleteRule = 'SET_NULL' THEN 'SET NULL'
WHEN @DeleteRule = 'SET_DEFAULT' THEN 'SET DEFAULT'
END

PRINT '=====> switching delete rule on ' + @ForeignKey + ' to ' + @switchBackTo;

BEGIN TRANSACTION
BEGIN TRY
EXEC('

ALTER TABLE ['+@TableOwner+'].[' + @TableName + ']
DROP CONSTRAINT '+@ForeignKey+';

ALTER TABLE ['+@TableOwner+'].[' + @TableName + '] ADD CONSTRAINT
'+@ForeignKey+' FOREIGN KEY
(
'+@ColumnName+'
) REFERENCES '+@ReferenceTableName+'
(
'+@ReferenceColumnName+'
) ON DELETE '+@switchBackTo+'
');

COMMIT TRANSACTION
END TRY
BEGIN CATCH
PRINT '=====> can''t change '+@ForeignKey + ' back to '+ @switchBackTo +', - ' +
CAST(ERROR_NUMBER() AS VARCHAR) + ' - ' + ERROR_MESSAGE();
ROLLBACK TRANSACTION
END CATCH;

FETCH NEXT FROM DataBaseTableRelationships
INTO @ForeignKey, @ColumnName, @ReferenceTableName, @ReferenceColumnName, @DeleteRule;
END;

CLOSE DataBaseTableRelationships;
DEALLOCATE DataBaseTableRelationships;

END
PRINT '';
PRINT '';

FETCH NEXT FROM DataBaseTables2
INTO @TableOwner,@TableName;
END
CLOSE DataBaseTables2;

DEALLOCATE DataBaseTables2;