java – 通过JDBC删除Derby中的所有约束

如何通过JDBC删除Derby数据库中的所有约束？ 最佳答案 您可以查询系统表SYS.SYSCONSTRAINTS,SYS.SYSTABLES和SYS.SYSSCHEMAS以获取给定模式的所有约束名称和相关表.

首先,关于这些表的几句话(从Re: System tables in Derby开始)：

SYSTABLES has one row for each table in the database. Its primary key is TABLEID,which contains system-generated values. The SCHEMAID is a foreign key column,which references SYSSCHEMAS.

SYSSCHEMAS has one row for each schema in the database. Its primary key is SCHEMAID.

…

SYSCONSTRAINTS has one row for each constraint in the database (primary,unique,foreign and check constraints). Its primary key is CONSTRAINTID,which is a system-generated value. The TABLEID column is a foreign key referring to SYSTABLES.TABLEID. The SCHEMAID column is a foreign key referring to SYSSCHEMAS.SCHEMAID.

所以你可以使用以下查询：

SELECT 
    C.CONSTRAINTNAME,T.TABLENAME 
FROM 
    SYS.SYSCONSTRAINTS C,SYS.SYSSCHEMAS S,SYS.SYSTABLES T 
WHERE 
    C.SCHEMAID = S.SCHEMAID 
AND 
    C.TABLEID = T.TABLEID
AND 
    S.SCHEMANAME = 'MYSCHEMA';

然后循环并构建相应的ALTER TABLE DROP CONSTRAINT语句.

参考

> Derby support for SQL-92 features

>表22.对SQL-92功能的支持：约束表

> Re: System tables in Derby

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