ORA-02266错误的批量解决方案

ORA-02266: unique/primary keys in table referenced by enabled foreign keys 这篇博客是很早之前总结的一篇文章，最近导数时使用 TRUNCATE 清理主表数据又遇到了这个错误，发现还有其它解决方案：

a) 禁用与主表相关的外键约束

b) TRUNCATE TABLE

c) 启用那些外键约束。

在实际操作中，发现使用上面的流程操作虽然正确，但是要写很多脚本，有些主表中的字段可能是多个表的外键约束。那么我们必须写多个脚本，那么我们必须使用脚本批量生成。具体如下所示：。

-- 生成禁用约束的脚本 , 解决 ORA-02266: unique/primary keys in table referenced by enabled foreign keys

SELECT DC.OWNER           AS "PARENT_TABLE_OWNER", 
       DC.TABLE_NAME      AS "PARENT_TABLE_NAME", 
       DC.CONSTRAINT_NAME AS "PRIMARY CONSTRAINT NAME", 
       DF.CONSTRAINT_NAME AS "REFERENCED CONSTRAINT NAME", 
       DF.OWNER           AS "CHILD_TABLE_OWNER", 
       DF.TABLE_NAME      AS "CHILD_TABLE_NAME" ,
       'ALTER TABLE ' || DF.OWNER  || '.' || DF.TABLE_NAME || ' DISABLE CONSTRAINT ' || DF.CONSTRAINT_NAME || ';'
FROM   DBA_CONSTRAINTS DC, 
       (SELECT C.OWNER, 
               C.CONSTRAINT_NAME, 
               C.R_CONSTRAINT_NAME, 
               C.TABLE_NAME 
        FROM   DBA_CONSTRAINTS C 
        WHERE  CONSTRAINT_TYPE = 'R') DF 
WHERE  DC.CONSTRAINT_NAME = DF.R_CONSTRAINT_NAME 
       AND DC.OWNER =UPPER('&OWNER')
       AND DC.TABLE_NAME=UPPER('&TABLE_NAME');

-- 生成启用约束的脚本 , 解决 ORA-02266: unique/primary keys in table referenced by enabled foreign keys

SELECT DC.OWNER           AS "PARENT_TABLE_OWNER", 
       DC.TABLE_NAME      AS "PARENT_TABLE_NAME", 
       DC.CONSTRAINT_NAME AS "PRIMARY CONSTRAINT NAME", 
       DF.CONSTRAINT_NAME AS "REFERENCED CONSTRAINT NAME", 
       DF.OWNER           AS "CHILD_TABLE_OWNER", 
       DF.TABLE_NAME      AS "CHILD_TABLE_NAME" ,
       'ALTER TABLE ' || DF.OWNER  || '.' || DF.TABLE_NAME || ' ENABLE CONSTRAINT ' || DF.CONSTRAINT_NAME || ';'
FROM   DBA_CONSTRAINTS DC, 
       (SELECT C.OWNER, 
               C.CONSTRAINT_NAME, 
               C.R_CONSTRAINT_NAME, 
               C.TABLE_NAME 
        FROM   DBA_CONSTRAINTS C 
        WHERE  CONSTRAINT_TYPE = 'R') DF 
WHERE  DC.CONSTRAINT_NAME = DF.R_CONSTRAINT_NAME 
       AND DC.OWNER =UPPER('&OWNER')
       AND DC.TABLE_NAME=UPPER('&TABLE_NAME');

原因分析：对于由 FOREIGN KEY 约束引用的表，不能使用 TRUNCATE TABLE ，因为 TRUNCATE 不会触发触发器，不会去验证任何约束。所以语法上是不允许的：有外键约束的表只能用DELETE，不能用TRUNCATE。

You cannot truncate a table with an enabled foreign key that points to it. Truncate does not fire any triggers, does not validate any constraints. It does not care of the child table is empty or not -- in this case the child table might actually not be empty.