將MySQL觸發器轉換爲SQLite

Question

我想知道是否有人可以幫助我將預更新觸發器從MySQL轉換爲SQLite。下面是MySQL的觸發器：

CREATE TRIGGER trigger_name 
    BEFORE UPDATE ON `table_name` 
    FOR EACH ROW 
BEGIN 
    IF (NEW.fk IS NOT NULL AND NEW.status < 50) 
    THEN 
    BEGIN 
     DECLARE obj_count INT(11); 
     SELECT COUNT(*) 
     INTO obj_count 
     FROM (SELECT id FROM table_name 
          WHERE `status` < 50 AND fk = NEW.fk 
          LIMIT 1) AS objs; 
     IF (obj_count > 0) 
     THEN 
     SIGNAL SQLSTATE '23000' SET MESSAGE_TEXT = "Error."; 
     END IF; 
    END; 
    END IF; 
END 

我undesrstanding是信號聲明需要重寫這樣的：SELECT RAISE(ABORT, 'Error.')

但也有，我有一個很難理解其他語法錯誤。

Answer 1

SQLite triggers既沒有IF也宣告：（BEFORE UPDATE OF fk, status ON table_name可能更有效）

CREATE TRIGGER trigger_name 
BEFORE UPDATE ON table_name 
FOR EACH ROW 
WHEN NEW.fk IS NOT NULL 
AND NEW.status < 50 
BEGIN 
    SELECT RAISE(ABORT, "Error.") 
    WHERE EXISTS (SELECT id 
        FROM table_name 
        WHERE status < 50 
        AND fk = NEW.fk); 
END;