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Come eliminare tutti i vincoli di chiave esterna in tutte le tabelle?

Ci sono molte informazioni sull'argomento dappertutto. Controlla questa risposta dettagliata di @Aaron Bertrand. Si parla di disabilitare temporaneamente le chiavi esterne ma leggendolo tutto e modificandolo a piacimento avrai un bel copione con cui giocare e ottenere molto.

Da parte mia posso proporre 2 diversi script per ottenere tutte le chiavi esterne. In entrambi i casi decommentare --EXEC (@SQL) per eseguire il tuo ALTER codice. Oppure puoi aspettare che stampi tutte le clausole alter e poi copia incolla per eseguirle.

Il primo usa il INFORMATION_SCHEMA per ottenere i vincoli:

DECLARE @SQL VARCHAR(MAX)=''
SELECT @SQL = @SQL + 'ALTER TABLE ' + QUOTENAME(FK.TABLE_SCHEMA) + '.' + QUOTENAME(FK.TABLE_NAME) + ' DROP CONSTRAINT [' + RTRIM(C.CONSTRAINT_NAME) +'];' + CHAR(13)
--SELECT K_Table = FK.TABLE_NAME, FK_Column = CU.COLUMN_NAME, PK_Table = PK.TABLE_NAME, PK_Column = PT.COLUMN_NAME, Constraint_Name = C.CONSTRAINT_NAME
  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

--EXEC (@SQL)

PRINT @SQL

Questo utilizza diverse viste di sistema e una tabella CTE.

DECLARE @SQL varchar(4000)=''
;WITH ReferencingFK AS 
(
    SELECT fk.Name AS 'FKName', OBJECT_NAME(fk.parent_object_id) 'ParentTable',
            cpa.name 'ParentColumnName', OBJECT_NAME(fk.referenced_object_id) 'ReferencedTable',
            cref.name 'ReferencedColumnName'
    FROM sys.foreign_keys fk
    INNER JOIN sys.foreign_key_columns fkc ON fkc.constraint_object_id = fk.object_id
    INNER JOIN sys.columns cpa ON fkc.parent_object_id = cpa.object_id AND fkc.parent_column_id = cpa.column_id
    INNER JOIN sys.columns cref ON fkc.referenced_object_id = cref.object_id AND fkc.referenced_column_id = cref.column_id
)
SELECT @SQL = @SQL + 'ALTER TABLE ' + ParentTable + ' DROP CONSTRAINT [' + RTRIM(FKName) +'];' + CHAR(13)
--SELECT FKName, ParentTable, ParentColumnName, ReferencedTable, ReferencedColumnName
  FROM ReferencingFK
 WHERE ReferencedTable = 'Employee'
 ORDER BY ParentTable, ReferencedTable, FKName

--EXEC (@SQL) 

PRINT @SQL