通过在 Postgresql 中存储在具有特殊字符的变量名中来删除约束

Question

我想删除名称未知的约束，所以我使用以下代码：

EXECUTE 'ALTER TABLE public."IntravenousTherapyAppointment" DROP CONSTRAINT '||fk_Name||';';

问题是 fk_Name 以“~”结尾，所以出现语法错误。

完整代码：

DO $$
DECLARE fk_Name TEXT;
BEGIN
    fk_Name := (SELECT
                tc.constraint_name
                FROM
                information_schema.table_constraints AS tc
                JOIN information_schema.key_column_usage AS kcu
                ON tc.constraint_name = kcu.constraint_name
                AND tc.table_schema = kcu.table_schema
                JOIN information_schema.constraint_column_usage AS ccu
                ON ccu.constraint_name = tc.constraint_name
                AND ccu.table_schema = tc.table_schema
                WHERE constraint_type = 'FOREIGN KEY' AND tc.table_name='IntravenousTherapyAppointment' AND ccu.table_name='MedicamentMeasurementUnit');
    IF fk_Name IS NOT NULL THEN
        EXECUTE 'ALTER TABLE public."IntravenousTherapyAppointment" DROP CONSTRAINT '||fk_Name||';';
    END IF;
END $$;

Answer 1

这应该可以解决您的问题：

DO $$
DECLARE fk_Name TEXT;
BEGIN
    fk_Name := (SELECT
                tc.constraint_name
                FROM
                information_schema.table_constraints AS tc
                JOIN information_schema.key_column_usage AS kcu
                ON tc.constraint_name = kcu.constraint_name
                AND tc.table_schema = kcu.table_schema
                JOIN information_schema.constraint_column_usage AS ccu
                ON ccu.constraint_name = tc.constraint_name
                AND ccu.table_schema = tc.table_schema
                WHERE constraint_type = 'FOREIGN KEY' AND tc.table_name='IntravenousTherapyAppointment' AND ccu.table_name='MedicamentMeasurementUnit');
    IF fk_Name IS NOT NULL THEN
        EXECUTE 'ALTER TABLE public."IntravenousTherapyAppointment" DROP CONSTRAINT "'||fk_Name||'";';
    END IF;
END $$;

P.S: Be careful while handling the objects/constraints having double quoted names.

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