SQL参考完整性触发

Question

CREATE TRIGGER FK_INTEGRITY_CHECK BEFORE INSERT ON sch_book_list FOR EACH ROW BEGIN SELECT CASE WHEN ((SELECT resource_cd FROM sch_resource WHERE resource_cd = NEW.resource_cd) IS NULL) THEN RAISE(ABORT, 'insert on table "sch_book_list" violates foreign key '|| 'constraint "FK9qti8knho9i047jd1lrwqwy2x"') END END;

这是我的触发代码，但是存在一些语法错误。我不知道错误是什么？

Answer 1

而不是使用CASE，您可以将计数存储在变量中并检查值，例如：

CREATE TRIGGER FK_INTEGRITY_CHECK
BEFORE INSERT ON sch_book_list
FOR EACH ROW BEGIN 
    DECLARE row_count INT;
    SET row_count = (SELECT COUNT(*) FROM sch_resource WHERE resource_cd = NEW.resource_cd)
    IF (row_count = 0) THEN
      RAISE(ABORT, 'insert on table "sch_book_list" violates foreign key '|| 'constraint "FK9qti8knho9i047jd1lrwqwy2x"');
    END IF;
END;