获取SQLite删除样结果

Question

我想通过在C ++中使用DELETE LIKE查询从表中删除几行。我知道该怎么做，并且有效。但我也想知道实际上删除了哪些行。有没有一种方法可以通过1个查询来做到这一点，或者不可能，并且唯一的方法是1.选择喜欢2.删除喜欢

Answer 1

作为SELECT-> DELETE的替代，您也可以使用TRIGGER。

下面的示例显示/演示了两种方法的相对通用的方法（这样效率稍低：-

DROP TABLE IF EXISTS mytable;
DROP TABLE IF EXISTS mytable_deletions;
DROP TABLE IF EXISTS mytable_deletions2;
DROP TRIGGER IF EXISTS mytable_deletions_trigger;

/* MAIN TABLE */
CREATE TABLE IF NOT EXISTS mytable(id INTEGER PRIMARY KEY, mydata TEXT);

/* CREATE TABLES TO RECORD DELETIONS (first for 1. select->delete the other for 2. trigger)*/
/* Note that these are created based upon the source table, with an additional column srowid so as to be able to definitively delete rows (extra column may not be needed) */
CREATE /*TEMP option? */ TABLE IF NOT EXISTS mytable_deletions AS SELECT 0 AS srowid,* FROM mytable WHERE mydata <> mydata;
CREATE /*TEMP option? */ TABLE IF NOT EXISTS mytable_deletions2 AS SELECT 0 AS srowid,* FROM mytable WHERE mydata <> mydata;
/* Create the BEFORE DELETE Trigger */
CREATE TRIGGER IF NOT EXISTS mytable_deletions_trigger BEFORE DELETE ON mytable
    BEGIN
        INSERT INTO mytable_deletions2 SELECT rowid AS srowid,* FROM mytable WHERE rowid = old.rowid;
    END
;
/* LOAD TESTING DATA */
INSERT INTO mytable (mydata) VALUES('A'),('B'),('C'),('D'),('E');

/* CLEAR PREVIOUS DELETIONS */
DELETE FROM mytable_deletions;
DELETE FROM mytable_deletions2;

/* 1. RECORD DELETIONS PRIOR AND DELETE ACCORDING TO RECORDED DELETIONS */
INSERT INTO mytable_deletions SELECT rowid AS srowid,* FROM mytable WHERE mydata >= 'C';
/* DO THE ACTUAL DELETIONS (will fire trigger 2.) */
DELETE FROM mytable WHERE rowid IN (SELECT srowid FROM mytable_deletions);


/* Display results from TRIGGER */
SELECT * FROM mytable;
SELECT * FROM mytable_deletions;
SELECT * FROM mytable_deletions2;

/* CLEANUP */
DROP TABLE IF EXISTS mytable;
DROP TABLE IF EXISTS mytable_deletions;
DROP TABLE IF EXISTS mytable_deletions2;
DROP TRIGGER IF EXISTS mytable_deletions_trigger;

在上面运行上述结果：-

剩余数据：-

已删除的行（选择->删除）

已删除的行（触发）