How to drop all Foreign Key constraints in all tables?

Question

I want to write sql command to drop all constraints in all tables. I searched on the internet and found the following which works fine if the database is small and not compl

Answer 1

I have improved the first script provided by @Yaroslav and the script provided by @Quandary so they now works for databases whose SQL query to drop all foreign keys one by one exceeds the size allocated for the SQL variable (4000 or MAX characters).

The altered scripts drop 5 foreign keys per iteration (just to be safe, implemented by adding TOP 5). The scripts stop when there is no foreign key left to drop (the SQL variable stays empty after running the SELECT).

First script by @Yaroslav

DECLARE @SQL varchar(4000)
IterationStart:
SET @SQL=''
SELECT TOP 5 @SQL = @SQL + 'ALTER TABLE ' + FK.TABLE_NAME + ' DROP CONSTRAINT [' + RTRIM(C.CONSTRAINT_NAME) +'];' + CHAR(13)
  FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS C
 INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS FK
    ON C.CONSTRAINT_NAME = FK.CONSTRAINT_NAME
 INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS PK
    ON C.UNIQUE_CONSTRAINT_NAME = PK.CONSTRAINT_NAME
 INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE CU
    ON C.CONSTRAINT_NAME = CU.CONSTRAINT_NAME
 INNER JOIN (
            SELECT i1.TABLE_NAME, i2.COLUMN_NAME
              FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS i1
             INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE i2
                ON i1.CONSTRAINT_NAME = i2.CONSTRAINT_NAME
            WHERE i1.CONSTRAINT_TYPE = 'PRIMARY KEY'
           ) PT
    ON PT.TABLE_NAME = PK.TABLE_NAME
IF @SQL <> ''
BEGIN
  EXEC(@SQL)
  GOTO IterationStart
END

Script by @Quandary

DECLARE @sql nvarchar(MAX) 

IterationStart:
SET @sql = '' 

SELECT TOP 5 @sql = @sql + 'ALTER TABLE ' + QUOTENAME(RC.CONSTRAINT_SCHEMA) 
    + '.' + QUOTENAME(KCU1.TABLE_NAME) 
    + ' DROP CONSTRAINT ' + QUOTENAME(rc.CONSTRAINT_NAME) + '; ' 
FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS AS RC 

INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS KCU1 
    ON KCU1.CONSTRAINT_CATALOG = RC.CONSTRAINT_CATALOG  
    AND KCU1.CONSTRAINT_SCHEMA = RC.CONSTRAINT_SCHEMA 
    AND KCU1.CONSTRAINT_NAME = RC.CONSTRAINT_NAME 

IF @SQL <> ''
BEGIN
  EXEC(@SQL)
  GOTO IterationStart
END