MySQL5.7的JSON基本操做

MySQL5.7的JSON基本操做

MySQL從5.7版本開始就支持JSON格式的數據，操做用起來挺方便的。

建表
在新建表時字段類型能夠直接設置爲json類型，好比咱們建立一張表：

mysql> CREATE TABLE `test_user`(`id` INT PRIMARY KEY AUTO_INCREMENT, `name` VARCHAR(50) NOT NULL, `info` JSON);

json類型字段能夠爲NULL

插入數據：

mysql> INSERT INTO test_user(`name`, `info`) VALUES('xiaoming','{"sex": 1, "age": 18, "nick_name": "小萌"}');

json類型的字段必須時一個有效的json字符串

能夠使用JSON_OBJECT()函數構造json對象：

mysql> INSERT INTO test_user(`name`, `info`) VALUES('xiaohua', JSON_OBJECT("sex", 0, "age", 17));

使用JSON_ARRAY()函數構造json數組：

mysql> INSERT INTO test_user(`name`, `info`) VALUES('xiaozhang', JSON_OBJECT("sex", 1, "age", 19, "tag", JSON_ARRAY(3,5,90)));

如今查看test_user表中的數據：

mysql> select * from test_user; 
+----+-----------+--------------------------------------------+ 
| id | name      | info                                       |
+----+-----------+--------------------------------------------+ 
|  1 | xiaoming  | {"age": 18, "sex": 1, "nick_name": "小萌"} | 
|  2 | xiaohua   | {"age": 17, "sex": 0}                      |
|  3 | xiaozhang | {"age": 19, "sex": 1, "tag": [3, 5, 90]}   | 
+----+-----------+--------------------------------------------+
3 rows in set (0.04 sec)

查詢
表達式： 對象爲json列->'$.鍵', 數組爲json列->'$.鍵[index]'

mysql> select name, info->'$.nick_name', info->'$.sex', info->'$.tag[0]' from test_user; 
+-----------+---------------------+---------------+------------------+ 
| name      | info->'$.nick_name' | info->'$.sex' | info->'$.tag[0]' | 
+-----------+---------------------+---------------+------------------+ 
| xiaoming  | "小萌"              | 1             | NULL             | 
| xiaohua   | NULL                | 0             | NULL             | 
| xiaozhang | NULL                | 1             | 3                | 
+-----------+---------------------+---------------+------------------+ 
3 rows in set (0.04 sec)

等價於：對象爲JSON_EXTRACT(json列 , '$.鍵')，數組爲JSON_EXTRACT(json列 , '$.鍵[index]')

mysql> select name, JSON_EXTRACT(info, '$.nick_name'), JSON_EXTRACT(info, '$.sex'), JSON_EXTRACT(info, '$.tag[0]')  from test_user;
 +-----------+-----------------------------------+-----------------------------+--------------------------------+ 
| name      | JSON_EXTRACT(info, '$.nick_name') | JSON_EXTRACT(info, '$.sex') | JSON_EXTRACT(info, '$.tag[0]') 
| +-----------+-----------------------------------+-----------------------------+--------------------------------+ 
| xiaoming  | "小萌"                            | 1                           | NULL                           |
| xiaohua   | NULL                              | 0                           | NULL                           | 
| xiaozhang | NULL                              | 1                           | 3                              | 
+-----------+-----------------------------------+-----------------------------+--------------------------------+ 
3 rows in set (0.04 sec)

不過看到上面"小萌"是帶雙引號的，這不是咱們想要的，能夠用JSON_UNQUOTE函數將雙引號去掉

mysql> select name, JSON_UNQUOTE(info->'$.nick_name') from test_user where name='xiaoming'; 
+----------+-----------------------------------+ 
| name     | JSON_UNQUOTE(info->'$.nick_name') | 
+----------+-----------------------------------+ 
| xiaoming | 小萌                              | 
+----------+-----------------------------------+ 
1 row in set (0.05 sec)

也能夠直接使用操做符->>

mysql> select name, info->>'$.nick_name' from test_user where name='xiaoming';
+----------+----------------------+ 
| name     | info->>'$.nick_name' | 
+----------+----------------------+ 
| xiaoming | 小萌                 | 
+----------+----------------------+ 
1 row in set (0.06 sec)

固然屬性也能夠做爲查詢條件

mysql> select name, info->>'$.nick_name' from test_user where info->'$.nick_name'='小萌'; 
+----------+----------------------+ 
| name     | info->>'$.nick_name' | 
+----------+----------------------+ 
| xiaoming | 小萌                 | 
+----------+----------------------+ 
1 row in set (0.05 sec)

值得一提的是，能夠經過虛擬列對JSON類型的指定屬性進行快速查詢。

建立虛擬列:

mysql> ALTER TABLE `test_user` ADD `nick_name` VARCHAR(50) GENERATED ALWAYS AS (info->>'$.nick_name') VIRTUAL;

注意用操做符->>

使用時和普通類型的列查詢是同樣:

mysql> select name,nick_name from test_user where nick_name='小萌'; 
+----------+-----------+ 
| name     | nick_name | 
+----------+-----------+ 
| xiaoming | 小萌      | 
+----------+-----------+ 
1 row in set (0.05 sec)

更新
使用JSON_INSERT()插入新值，但不會覆蓋已經存在的值

mysql> UPDATE test_user SET info = JSON_INSERT(info, '$.sex', 1, '$.nick_name', '小花') where id=2;

看下結果

mysql> select * from test_user where id=2; 
+----+---------+--------------------------------------------+-----------+ 
| id | name    | info                                       | nick_name | 
+----+---------+--------------------------------------------+-----------+ 
|  2 | xiaohua | {"age": 17, "sex": 0, "nick_name": "小花"} | 小花      | 
+----+---------+--------------------------------------------+-----------+ 
1 row in set (0.06 sec)

使用JSON_SET()插入新值，並覆蓋已經存在的值

mysql> UPDATE test_user SET info = JSON_INSERT(info, '$.sex', 0, '$.nick_name', '小張') where id=3;

看下結果

mysql> select * from test_user where id=3; 
+----+-----------+---------------------------------------------------------------+-----------+ 
| id | name      | info                                                          | nick_name | 
+----+-----------+---------------------------------------------------------------+-----------+ 
|  3 | xiaozhang | {"age": 19, "sex": 1, "tag": [3, 5, 90], "nick_name": "小張"} | 小張      | 
+----+-----------+---------------------------------------------------------------+-----------+ 
1 row in set (0.06 sec)

使用JSON_REPLACE()只替換存在的值

mysql> UPDATE test_user SET info = JSON_REPLACE(info, '$.sex', 1, '$.tag', '[1,2,3]') where id=2;

看下結果

mysql> select * from test_user where id=2; 
+----+---------+--------------------------------------------+-----------+ 
| id | name    | info                                       | nick_name | 
+----+---------+--------------------------------------------+-----------+ 
|  2 | xiaohua | {"age": 17, "sex": 1, "nick_name": "小花"} | 小花      | 
+----+---------+--------------------------------------------+-----------+ 
1 row in set (0.06 sec)

能夠看到tag沒有更新進去

刪除

使用JSON_REMOVE()刪除JSON元素

mysql> UPDATE test_user SET info = JSON_REMOVE(info, '$.sex', '$.tag') where id=1;

看下結果

mysql> select * from test_user where id=1; 
+----+----------+----------------------------------+-----------+ 
| id | name     | info                             | nick_name | 
+----+----------+----------------------------------+-----------+ 
|  1 | xiaoming | {"age": 18, "nick_name": "小萌"} | 小萌      | 
+----+----------+----------------------------------+-----------+ 
1 row in set (0.05 sec)