删除重复的外键

Question

我有大约100个表,其中所有表都有重复的外键约束.

有没有办法可以摆脱它？是否有查询可以为我提供所有重复的密钥？

Answer 1

我在这里使用这个T-SQL脚本来检测可能重复的FK约束 - 它还ALTER TABLE...DROP CONSTRAINT在最后一个输出列中生成必要的语句.

您无法可靠地自动检测并选择要丢弃的多个FK约束中的哪一个 - 因此您基本上只能检测它们,然后手动选择要丢弃的那些(使用我的查询生成的drop语句).

;WITH FKData AS
(
    SELECT  
        fk.parent_object_id,
        fkc.parent_column_id,
        fk.referenced_object_id,
        fkc.referenced_column_id,
        FKCount = COUNT(*)
    FROM 
         sys.foreign_keys fk
    INNER JOIN 
         sys.foreign_key_columns fkc ON fkc.constraint_object_id = fk.object_id
    GROUP BY 
         fk.parent_object_id, fkc.parent_column_id, fk.referenced_object_id, fkc.referenced_column_id
    HAVING 
         COUNT(*) > 1
),
DuplicateFK AS
(
    SELECT  
        FKName = fk.Name,
            ParentSchema = s1.Name,
        ParentTable = t1.Name,
        ParentColumn = c1.Name,
        ReferencedTable = t2.Name,
        ReferencedColumn = c2.Name 
    FROM 
        sys.foreign_keys fk
    INNER JOIN 
        sys.foreign_key_columns fkc ON fkc.constraint_object_id = fk.object_id
    INNER JOIN 
        FKData f ON fk.parent_object_id = f.parent_object_id 
                 AND fk.referenced_object_id = f.referenced_object_id 
                 AND fkc.parent_column_id = f.parent_column_id
                 AND fkc.referenced_column_id = f.referenced_column_id
    INNER JOIN 
        sys.tables t1 ON f.parent_object_id = t1.object_id
    INNER JOIN 
        sys.columns c1 ON f.parent_object_id = c1.object_id AND f.parent_column_id = c1.column_id
INNER JOIN 
    sys.schemas s1 ON t1.schema_id = s1.schema_id   
    INNER JOIN 
        sys.tables t2 ON f.referenced_object_id = t2.object_id
    INNER JOIN 
        sys.columns c2 ON f.referenced_object_id = c2.object_id AND f.referenced_column_id = c2.column_id
)
SELECT
    FKName,
    ParentSchema, ParentTable, ParentColumn, 
    ReferencedTable, ReferencedColumn,
    DropStmt = 'ALTER TABLE ' + ParentSchema + '.' + ParentTable + 
               ' DROP CONSTRAINT ' + FKName
FROM 
    DuplicateFK