Mysql將查詢結(jié)果集轉(zhuǎn)換為JSON數(shù)據(jù) 前言學生表學生成績表查詢單個學生各科成績（轉(zhuǎn)換為對象JSON串并用逗號拼接）將單個學生各科成績轉(zhuǎn)換為數(shù)組JSON串將數(shù)組串作為value并設(shè)置key兩張表聯(lián)合查詢(最終SQL，每個學生各科成績)最終結(jié)果
前言
我們經(jīng)常會有這樣一種需求，一對關(guān)聯(lián)關(guān)系表，一對多的關(guān)系，使用一條sql語句查詢兩張表的所有記錄，例：一張學生表，一張學生各科成績表，我們想要用一條SQL查詢出每個學生各科成績；
學生表
CREATE TABLE IF NOT EXISTS `student`(
`id` INT UNSIGNED AUTO_INCREMENT,
`name` VARCHAR(100) NOT NULL
PRIMARY KEY ( `id` )
)ENGINE=InnoDB DEFAULT CHARSET=utf8;
INSERT INTO student( id, name ) VALUES ( 1, '張三' );
INSERT INTO student( id, name ) VALUES ( 2, '李四' );
學生成績表
CREATE TABLE IF NOT EXISTS `score`(
`id` INT UNSIGNED AUTO_INCREMENT,
`name` VARCHAR(100) NOT NULL
`student_id` INT(100) NOT NULL,
`score` VARCHAR(100) NOT NULL
PRIMARY KEY ( `id` )
)ENGINE=InnoDB DEFAULT CHARSET=utf8;
INSERT INTO score( id, name, student_id, score) VALUES ( 1, '數(shù)學', 1, '95.5' );
INSERT INTO score( id, name, student_id, score) VALUES ( 2, '語文', 1, '99.5' );
INSERT INTO score( id, name, student_id, score) VALUES ( 3, '數(shù)學', 2, '95.5' );
INSERT INTO score( id, name, student_id, score) VALUES ( 4, '語文', 2, '88' );
查詢單個學生各科成績（轉(zhuǎn)換為對象JSON串并用逗號拼接）
SELECT GROUP_CONCAT(JSON_OBJECT(
'id',id,'name',name,'student_id',student_id, 'score', score)) as scores FROM scroe where student_id = 1;
## 查詢結(jié)果
## {"id": 1, "name": "數(shù)學", "student_id": 1, "score": "95.5"},{"id": 2, "name": "語文", "student_id": 1, "score": "99.5"}
將單個學生各科成績轉(zhuǎn)換為數(shù)組JSON串
SELECT CONCAT('[', GROUP_CONCAT(JSON_OBJECT(
'id',id,'name',name,'student_id',student_id, 'score', score)), ']') as scores FROM scroe where student_id = 1
## 查詢結(jié)果
## [{"id": 1, "name": "數(shù)學", "student_id": 1, "score": "95.5"},{"id": 2, "name": "語文", "student_id": 1, "score": "99.5"}]
將數(shù)組串作為value并設(shè)置key
SELECT CONCAT('{"scoreData":[', GROUP_CONCAT(JSON_OBJECT(
'id',id,'name',name,'student_id',student_id, 'score', score)), ']}') as scores FROM scroe where student_id = 1
## 查詢結(jié)果
## {"scoreData": [{"id": 1, "name": "數(shù)學", "student_id": 1, "score": "95.5"},{"id": 2, "name": "語文", "student_id": 1, "score": "99.5"}]}
兩張表聯(lián)合查詢(最終SQL，每個學生各科成績)
SELECT id, name,
(SELECT CONCAT('[', GROUP_CONCAT(JSON_OBJECT(
'id',id,'name',name,'student_id',student_id, 'score', score)), ']') as scores FROM scroe WHERE student_id = stu.id) AS scores
from student stu
## [{"id": 1, "name": "數(shù)學", "student_id": 1, "score": "95.5"},{"id": 2, "name": "語文", "student_id": 1, "score": "99.5"}]
最終結(jié)果
| ID |
NAME |
SCORES |
| 1 |
張三 |
[{“id”: 1, “name”: “數(shù)學”, “student_id”: 1, “score”: “95.5”},{“id”: 2, “name”: “語文”, “student_id”: 1, “score”: “99.5”}] |
| 2 |
李四 |
[{“id”: 3, “name”: “數(shù)學”, “student_id”: 1, “score”: “95.5”},{“id”:4, “name”: “語文”, “student_id”: 1, “score”: “88”}] |
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