Question

我的查询在使用子查询时不起作用

我有商店产品表

"auto_id"   "category"  "name"  "last_update"
"1"     "1"     "BOOK"  "2018-12-06 17:35:19"
"2"     "1"     "BOOK"  "2018-09-26 10:45:08"
"7"     "1"     "PENCIL"    "2018-10-09 08:50:40"
"8"     "1"     "BOOK"  "2018-12-04 14:39:32"
"9"     "4"     "RULER" "2018-10-11 06:45:50"
"10"        "2"     "PAPER" "2018-11-13 08:35:34"
"11"        "1"     "Pen"   "2018-11-28 11:54:18"
"12"        "2"     "ERASER"    "2018-11-28   12:06:36"
"13"        "2"     "PAPER F4"  "2018-12-10 16:43:08"
"14"        "2"     "PAPER F4"  "2018-12-05 05:53:30"
"15"        "1"     "BOOK"  "2018-12-10 16:42:37"




SELECT GROUP_CONCAT(DISTINCT(CONCAT('"',z.name,'"')))  AS n
FROM shop_product z 
WHERE z.category = 2 AND DATE(z.last_update) BETWEEN '2018-07-01' AND '2018-12-31'

和结果

"PAPER F4","PAPER","ERASER"

以及在没有结果的情况下运行完整查询的地方

SELECT a.id FROM shop_product AS a WHERE a.name IN (
SELECT GROUP_CONCAT(DISTINCT(CONCAT('"',z.name,'"')))  AS n
FROM shop_product z 
WHERE z.category = 2 AND DATE(z.last_update) BETWEEN '2018-07-01'AND '2018-12-31')

如果使用结果字符串之前的子查询来更改子查询

SELECT a.id FROM shop_product AS a WHERE a.name IN ("PAPER F4","PAPER","ERASER")

可以显示结果。

如何使用子查询获取数据

Answer 1

您不需要concat（）和group_concat（）函数成为垃圾。只需使用简单的子选择即可。

SELECT a.`auto_id`, a.`category`, a.`name`, a.`last_update`
FROM shop_product a 
WHERE name IN(
    SELECT z.`name`
    FROM shop_product z
    WHERE z.category = 2 
    AND DATE(z.last_update) 
    BETWEEN '2018-07-01' AND '2018-12-31'
)

（SubQuery）中的哪里不起作用的MySQL查询

1 个答案: