SQL 条件插入

Question

我正在使用 MySQL。如何根据相关数据的验证将 INSERT 执行到 table 中？原谅人为的例子。

如果我的 table 是：

> SELECT * FROM colors;
id color  owner
-- ------ -----
10 red    2
11 banana 6
12 blue   9

和

> SELECT * FROM fruit;
id  color_id  name
--  --------  -------
59  10        cherry
60  12        blueberry

其中 fruit.color 是 colors.id

的外键

我想插入有关香蕉的信息，但前提是颜色的所有者是 6。这是原始插入：

INSERT INTO
    fruit
    (color_id, name)
VALUES
    (11, 'banana');

我想做类似的事情：

INSERT INTO
    fruit
    (color_id, name)
VALUES
    (11, 'banana')

-- ??? I have no idea what to put here ???
ONLY IF (
    (SELECT COUNT(*) FROM fruit
    INNER JOIN colors ON fruit.color_id = colors.id
    AND   colors.id     = 11
    WHERE colors.owners = 6) >= 1
)

最后一个条款显然不是真的，但我不知道该怎么做。如果我要插入的 color_id 的 owner 列等于我提供的值，这个想法只是插入值。

帮忙？

Answer 1

您可以尝试这样的操作：

insert into fruit (color_id, name)
select 11, 'banana'
where (select count(*) from fruit join colors on fruit.color_id = colors.id
where colors.id = 11 and colors.owner = 6) >= 1;

或等效

insert into fruit (color_id, name)
select 11, 'banana'
where exists 
(select * from fruit join colors on fruit.color_id = colors.id
where colors.id = 11 and colors.owner = 6);

Answer 2

这对你有用吗？

IF (SELECT COUNT(*) FROM fruit
    INNER JOIN colors ON fruit.color_id = colors.id
    AND   colors.id     = 11
    WHERE colors.owners = 6) >= 1
THEN
   INSERT INTO fruit
   (color_id, name)
   VALUES
   (11, 'banana');
END IF;

SQL 条件插入

SQL Conditional INSERT

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