MySQL处理JSON常见函数的使用？

2023-07-04 13:51:41 136

官方文档：JSONFunctions

Name Description JSON_APPEND() AppenddatatoJSONdocument JSON_ARRAY() CreateJSONarray JSON_ARRAY_APPEND() AppenddatatoJSONdocument JSON_ARRAY_INSERT() InsertintoJSONarray -> ReturnvaluefromJSONcolumnafterevaluatingpath;equivalenttoJSON_EXTRACT(). JSON_CONTAINS() WhetherJSONdocumentcontainsspecificobjectatpath JSON_CONTAINS_PATH() WhetherJSONdocumentcontainsanydataatpath JSON_DEPTH() MaximumdepthofJSONdocument JSON_EXTRACT() ReturndatafromJSONdocument ->> ReturnvaluefromJSONcolumnafterevaluatingpathandunquotingtheresult;equivalenttoJSON_UNQUOTE(JSON_EXTRACT()). JSON_INSERT() InsertdataintoJSONdocument JSON_KEYS() ArrayofkeysfromJSONdocument JSON_LENGTH() NumberofelementsinJSONdocument JSON_MERGE() MergeJSONdocuments JSON_OBJECT() CreateJSONobject JSON_QUOTE() QuoteJSONdocument JSON_REMOVE() RemovedatafromJSONdocument JSON_REPLACE() ReplacevaluesinJSONdocument JSON_SEARCH() PathtovaluewithinJSONdocument JSON_SET() InsertdataintoJSONdocument JSON_TYPE() TypeofJSONvalue JSON_UNQUOTE() UnquoteJSONvalue JSON_VALID() WhetherJSONvalueisvalid

1.概述

MySQL里的json分为jsonarray和jsonobject。$表示整个json对象，在索引数据时用下标(对于jsonarray，从0开始)或键值(对于jsonobject，含有特殊字符的key要用"括起来，比如$."myname")。

例如：[3,{"a":[5,6],"b":10},[99,100]]，那么：

$[0]：3

$[1]：{"a":[5,6],"b":10}

$[2]：[99,100]

$[3]：NULL

$[1].a：[5,6]

$[1].a[1]：6

$[1].b：10

$[2][0]：99

2.比较规则

json中的数据可以用=,<,<=,>,>=,<>,!=,and<=>进行比较。但json里的数据类型可以是多样的，那么在不同类型之间进行比较时，就有优先级了，高优先级的要大于低优先级的（可以用JSON_TYPE()函数查看类型）。优先级从高到低如下：

BLOB
BIT
OPAQUE
DATETIME
TIME
DATE
BOOLEAN
ARRAY
OBJECT
STRING
INTEGER,DOUBLE
NULL

3.常用函数

3.1创建函数

3.1.1JSON_ARRAY

JSON_ARRAY(val1,val2,val3...)

生成一个包含指定元素的json数组。

mysql>SELECTJSON_ARRAY(1,"abc",NULL,TRUE,CURTIME());
+---------------------------------------------+
|JSON_ARRAY(1,"abc",NULL,TRUE,CURTIME())|
+---------------------------------------------+
|[1,"abc",null,true,"11:30:24.000000"]|
+---------------------------------------------+

3.1.2JSON_OBJECT

JSON_OBJECT(key1,val1,key2,val2...)

生成一个包含指定K-V对的jsonobject。如果有key为NULL或参数个数为奇数，则抛错。

mysql>SELECTJSON_OBJECT('id',87,'name','carrot');
+-----------------------------------------+
|JSON_OBJECT('id',87,'name','carrot')|
+-----------------------------------------+
|{"id":87,"name":"carrot"}|
+-----------------------------------------+

3.1.3JSON_QUOTE

JSON_QUOTE(json_val)

将json_val用"号括起来。

mysql>SELECTJSON_QUOTE('null'),JSON_QUOTE('"null"');
+--------------------+----------------------+
|JSON_QUOTE('null')|JSON_QUOTE('"null"')|
+--------------------+----------------------+
|"null"|"\"null\""|
+--------------------+----------------------+
mysql>SELECTJSON_QUOTE('[1,2,3]');
+-------------------------+
|JSON_QUOTE('[1,2,3]')|
+-------------------------+
|"[1,2,3]"|
+-------------------------+

3.1.4CONVERT

CONVERT(json_string,JSON)

mysql>selectCONVERT('{"mail":"amy@gmail.com","name":"Amy"}',JSON);
+----------------------------------------------------------+
|CONVERT('{"mail":"amy@gmail.com","name":"Amy"}',JSON)|
+----------------------------------------------------------+
|{"mail":"amy@gmail.com","name":"Amy"}|
+----------------------------------------------------------+

3.2查询函数

3.2.1JSON_CONTAINS

JSON_CONTAINS(json_doc,val[,path])

查询json文档是否在指定path包含指定的数据，包含则返回1，否则返回0。如果有参数为NULL或path不存在，则返回NULL。

mysql>SET@j='{"a":1,"b":2,"c":{"d":4}}';
mysql>SET@j2='1';
mysql>SELECTJSON_CONTAINS(@j,@j2,'$.a');
+-------------------------------+
|JSON_CONTAINS(@j,@j2,'$.a')|
+-------------------------------+
|1|
+-------------------------------+
mysql>SELECTJSON_CONTAINS(@j,@j2,'$.b');
+-------------------------------+
|JSON_CONTAINS(@j,@j2,'$.b')|
+-------------------------------+
|0|
+-------------------------------+

mysql>SET@j2='{"d":4}';
mysql>SELECTJSON_CONTAINS(@j,@j2,'$.a');
+-------------------------------+
|JSON_CONTAINS(@j,@j2,'$.a')|
+-------------------------------+
|0|
+-------------------------------+
mysql>SELECTJSON_CONTAINS(@j,@j2,'$.c');
+-------------------------------+
|JSON_CONTAINS(@j,@j2,'$.c')|
+-------------------------------+
|1|
+-------------------------------+

3.2.2JSON_CONTAINS_PATH

JSON_CONTAINS_PATH(json_doc,one_or_all,path[,path]...)

查询是否存在指定路径，存在则返回1，否则返回0。如果有参数为NULL，则返回NULL。

one_or_all只能取值"one"或"all"，one表示只要有一个存在即可；all表示所有的都存在才行。

mysql>SET@j='{"a":1,"b":2,"c":{"d":4}}';
mysql>SELECTJSON_CONTAINS_PATH(@j,'one','$.a','$.e');
+---------------------------------------------+
|JSON_CONTAINS_PATH(@j,'one','$.a','$.e')|
+---------------------------------------------+
|1|
+---------------------------------------------+
mysql>SELECTJSON_CONTAINS_PATH(@j,'all','$.a','$.e');
+---------------------------------------------+
|JSON_CONTAINS_PATH(@j,'all','$.a','$.e')|
+---------------------------------------------+
|0|
+---------------------------------------------+
mysql>SELECTJSON_CONTAINS_PATH(@j,'one','$.c.d');
+----------------------------------------+
|JSON_CONTAINS_PATH(@j,'one','$.c.d')|
+----------------------------------------+
|1|
+----------------------------------------+
mysql>SELECTJSON_CONTAINS_PATH(@j,'one','$.a.d');
+----------------------------------------+
|JSON_CONTAINS_PATH(@j,'one','$.a.d')|
+----------------------------------------+
|0|
+----------------------------------------+

3.2.3JSON_EXTRACT

JSON_EXTRACT(json_doc,path[,path]...)

从json文档里抽取数据。如果有参数有NULL或path不存在，则返回NULL。如果抽取出多个path，则返回的数据封闭在一个jsonarray里。

mysql>SELECTJSON_EXTRACT('[10,20,[30,40]]','$[1]');
+--------------------------------------------+
|JSON_EXTRACT('[10,20,[30,40]]','$[1]')|
+--------------------------------------------+
|20|
+--------------------------------------------+
mysql>SELECTJSON_EXTRACT('[10,20,[30,40]]','$[1]','$[0]');
+----------------------------------------------------+
|JSON_EXTRACT('[10,20,[30,40]]','$[1]','$[0]')|
+----------------------------------------------------+
|[20,10]|
+----------------------------------------------------+
mysql>SELECTJSON_EXTRACT('[10,20,[30,40]]','$[2][*]');
+-----------------------------------------------+
|JSON_EXTRACT('[10,20,[30,40]]','$[2][*]')|
+-----------------------------------------------+
|[30,40]|
+-----------------------------------------------+

在MySQL5.7.9+里可以用"->"替代。

mysql>SELECTc,JSON_EXTRACT(c,"$.id"),g
>FROMjemp
>WHEREJSON_EXTRACT(c,"$.id")>1
>ORDERBYJSON_EXTRACT(c,"$.name");
+-------------------------------+-----------+------+
|c|c->"$.id"|g|
+-------------------------------+-----------+------+
|{"id":"3","name":"Barney"}|"3"|3|
|{"id":"4","name":"Betty"}|"4"|4|
|{"id":"2","name":"Wilma"}|"2"|2|
+-------------------------------+-----------+------+
3rowsinset(0.00sec)

mysql>SELECTc,c->"$.id",g
>FROMjemp
>WHEREc->"$.id">1
>ORDERBYc->"$.name";
+-------------------------------+-----------+------+
|c|c->"$.id"|g|
+-------------------------------+-----------+------+
|{"id":"3","name":"Barney"}|"3"|3|
|{"id":"4","name":"Betty"}|"4"|4|
|{"id":"2","name":"Wilma"}|"2"|2|
+-------------------------------+-----------+------+
3rowsinset(0.00sec)

在MySQL5.7.13+，还可以用"->>"表示去掉抽取结果的"号，下面三种效果是一样的：

JSON_UNQUOTE(JSON_EXTRACT(column,path))
JSON_UNQUOTE(column->path)
column->>path

mysql>SELECT*FROMjempWHEREg>2;
+-------------------------------+------+
|c|g|
+-------------------------------+------+
|{"id":"3","name":"Barney"}|3|
|{"id":"4","name":"Betty"}|4|
+-------------------------------+------+
2rowsinset(0.01sec)

mysql>SELECTc->'$.name'ASname
->FROMjempWHEREg>2;
+----------+
|name|
+----------+
|"Barney"|
|"Betty"|
+----------+
2rowsinset(0.00sec)

mysql>SELECTJSON_UNQUOTE(c->'$.name')ASname
->FROMjempWHEREg>2;
+--------+
|name|
+--------+
|Barney|
|Betty|
+--------+
2rowsinset(0.00sec)

mysql>SELECTc->>'$.name'ASname
->FROMjempWHEREg>2;
+--------+
|name|
+--------+
|Barney|
|Betty|
+--------+
2rowsinset(0.00sec)

3.2.4JSON_KEYS

JSON_KEYS(json_doc[,path])

获取json文档在指定路径下的所有键值，返回一个jsonarray。如果有参数为NULL或path不存在，则返回NULL。

mysql>SELECTJSON_KEYS('{"a":1,"b":{"c":30}}');
+---------------------------------------+
|JSON_KEYS('{"a":1,"b":{"c":30}}')|
+---------------------------------------+
|["a","b"]|
+---------------------------------------+
mysql>SELECTJSON_KEYS('{"a":1,"b":{"c":30}}','$.b');
+----------------------------------------------+
|JSON_KEYS('{"a":1,"b":{"c":30}}','$.b')|
+----------------------------------------------+
|["c"]|
+----------------------------------------------+

3.2.5JSON_SEARCH

JSON_SEARCH(json_doc,one_or_all,search_str[,escape_char[,path]...])

查询包含指定字符串的paths，并作为一个jsonarray返回。如果有参数为NUL或path不存在，则返回NULL。

one_or_all："one"表示查询到一个即返回；"all"表示查询所有。
search_str：要查询的字符串。可以用LIKE里的'%'或‘_'匹配。
path：在指定path下查。

mysql>SET@j='["abc",[{"k":"10"},"def"],{"x":"abc"},{"y":"bcd"}]';

mysql>SELECTJSON_SEARCH(@j,'one','abc');
+-------------------------------+
|JSON_SEARCH(@j,'one','abc')|
+-------------------------------+
|"$[0]"|
+-------------------------------+

mysql>SELECTJSON_SEARCH(@j,'all','abc');
+-------------------------------+
|JSON_SEARCH(@j,'all','abc')|
+-------------------------------+
|["$[0]","$[2].x"]|
+-------------------------------+

mysql>SELECTJSON_SEARCH(@j,'all','ghi');
+-------------------------------+
|JSON_SEARCH(@j,'all','ghi')|
+-------------------------------+
|NULL|
+-------------------------------+

mysql>SELECTJSON_SEARCH(@j,'all','10');
+------------------------------+
|JSON_SEARCH(@j,'all','10')|
+------------------------------+
|"$[1][0].k"|
+------------------------------+

mysql>SELECTJSON_SEARCH(@j,'all','10',NULL,'$');
+-----------------------------------------+
|JSON_SEARCH(@j,'all','10',NULL,'$')|
+-----------------------------------------+
|"$[1][0].k"|
+-----------------------------------------+

mysql>SELECTJSON_SEARCH(@j,'all','10',NULL,'$[*]');
+--------------------------------------------+
|JSON_SEARCH(@j,'all','10',NULL,'$[*]')|
+--------------------------------------------+
|"$[1][0].k"|
+--------------------------------------------+

mysql>SELECTJSON_SEARCH(@j,'all','10',NULL,'$**.k');
+---------------------------------------------+
|JSON_SEARCH(@j,'all','10',NULL,'$**.k')|
+---------------------------------------------+
|"$[1][0].k"|
+---------------------------------------------+

mysql>SELECTJSON_SEARCH(@j,'all','10',NULL,'$[*][0].k');
+-------------------------------------------------+
|JSON_SEARCH(@j,'all','10',NULL,'$[*][0].k')|
+-------------------------------------------------+
|"$[1][0].k"|
+-------------------------------------------------+

mysql>SELECTJSON_SEARCH(@j,'all','10',NULL,'$[1]');
+--------------------------------------------+
|JSON_SEARCH(@j,'all','10',NULL,'$[1]')|
+--------------------------------------------+
|"$[1][0].k"|
+--------------------------------------------+

mysql>SELECTJSON_SEARCH(@j,'all','10',NULL,'$[1][0]');
+-----------------------------------------------+
|JSON_SEARCH(@j,'all','10',NULL,'$[1][0]')|
+-----------------------------------------------+
|"$[1][0].k"|
+-----------------------------------------------+

mysql>SELECTJSON_SEARCH(@j,'all','abc',NULL,'$[2]');
+---------------------------------------------+
|JSON_SEARCH(@j,'all','abc',NULL,'$[2]')|
+---------------------------------------------+
|"$[2].x"|
+---------------------------------------------+

mysql>SELECTJSON_SEARCH(@j,'all','%a%');
+-------------------------------+
|JSON_SEARCH(@j,'all','%a%')|
+-------------------------------+
|["$[0]","$[2].x"]|
+-------------------------------+

mysql>SELECTJSON_SEARCH(@j,'all','%b%');
+-------------------------------+
|JSON_SEARCH(@j,'all','%b%')|
+-------------------------------+
|["$[0]","$[2].x","$[3].y"]|
+-------------------------------+

mysql>SELECTJSON_SEARCH(@j,'all','%b%',NULL,'$[0]');
+---------------------------------------------+
|JSON_SEARCH(@j,'all','%b%',NULL,'$[0]')|
+---------------------------------------------+
|"$[0]"|
+---------------------------------------------+

mysql>SELECTJSON_SEARCH(@j,'all','%b%',NULL,'$[2]');
+---------------------------------------------+
|JSON_SEARCH(@j,'all','%b%',NULL,'$[2]')|
+---------------------------------------------+
|"$[2].x"|
+---------------------------------------------+

mysql>SELECTJSON_SEARCH(@j,'all','%b%',NULL,'$[1]');
+---------------------------------------------+
|JSON_SEARCH(@j,'all','%b%',NULL,'$[1]')|
+---------------------------------------------+
|NULL|
+---------------------------------------------+

mysql>SELECTJSON_SEARCH(@j,'all','%b%','','$[1]');
+-------------------------------------------+
|JSON_SEARCH(@j,'all','%b%','','$[1]')|
+-------------------------------------------+
|NULL|
+-------------------------------------------+

mysql>SELECTJSON_SEARCH(@j,'all','%b%','','$[3]');
+-------------------------------------------+
|JSON_SEARCH(@j,'all','%b%','','$[3]')|
+-------------------------------------------+
|"$[3].y"|
+-------------------------------------------+

3.3修改函数

3.3.1JSON_APPEND/JSON_ARRAY_APPEND

JSON_ARRAY_APPEND(json_doc,path,val[,path,val]...)

在指定path的jsonarray尾部追加val。如果指定path是一个jsonobject，则将其封装成一个jsonarray再追加。如果有参数为NULL，则返回NULL。

mysql>SET@j='["a",["b","c"],"d"]';
mysql>SELECTJSON_ARRAY_APPEND(@j,'$[1]',1);
+----------------------------------+
|JSON_ARRAY_APPEND(@j,'$[1]',1)|
+----------------------------------+
|["a",["b","c",1],"d"]|
+----------------------------------+
mysql>SELECTJSON_ARRAY_APPEND(@j,'$[0]',2);
+----------------------------------+
|JSON_ARRAY_APPEND(@j,'$[0]',2)|
+----------------------------------+
|[["a",2],["b","c"],"d"]|
+----------------------------------+
mysql>SELECTJSON_ARRAY_APPEND(@j,'$[1][0]',3);
+-------------------------------------+
|JSON_ARRAY_APPEND(@j,'$[1][0]',3)|
+-------------------------------------+
|["a",[["b",3],"c"],"d"]|
+-------------------------------------+

mysql>SET@j='{"a":1,"b":[2,3],"c":4}';
mysql>SELECTJSON_ARRAY_APPEND(@j,'$.b','x');
+------------------------------------+
|JSON_ARRAY_APPEND(@j,'$.b','x')|
+------------------------------------+
|{"a":1,"b":[2,3,"x"],"c":4}|
+------------------------------------+
mysql>SELECTJSON_ARRAY_APPEND(@j,'$.c','y');
+--------------------------------------+
|JSON_ARRAY_APPEND(@j,'$.c','y')|
+--------------------------------------+
|{"a":1,"b":[2,3],"c":[4,"y"]}|
+--------------------------------------+

mysql>SET@j='{"a":1}';
mysql>SELECTJSON_ARRAY_APPEND(@j,'$','z');
+---------------------------------+
|JSON_ARRAY_APPEND(@j,'$','z')|
+---------------------------------+
|[{"a":1},"z"]|
+---------------------------------+

3.3.2JSON_ARRAY_INSERT

JSON_ARRAY_INSERT(json_doc,path,val[,path,val]...)

在path指定的jsonarray元素插入val，原位置及以右的元素顺次右移。如果path指定的数据非jsonarray元素，则略过此val；如果指定的元素下标超过jsonarray的长度，则插入尾部。

mysql>SET@j='["a",{"b":[1,2]},[3,4]]';
mysql>SELECTJSON_ARRAY_INSERT(@j,'$[1]','x');
+------------------------------------+
|JSON_ARRAY_INSERT(@j,'$[1]','x')|
+------------------------------------+
|["a","x",{"b":[1,2]},[3,4]]|
+------------------------------------+
mysql>SELECTJSON_ARRAY_INSERT(@j,'$[100]','x');
+--------------------------------------+
|JSON_ARRAY_INSERT(@j,'$[100]','x')|
+--------------------------------------+
|["a",{"b":[1,2]},[3,4],"x"]|
+--------------------------------------+
mysql>SELECTJSON_ARRAY_INSERT(@j,'$[1].b[0]','x');
+-----------------------------------------+
|JSON_ARRAY_INSERT(@j,'$[1].b[0]','x')|
+-----------------------------------------+
|["a",{"b":["x",1,2]},[3,4]]|
+-----------------------------------------+
mysql>SELECTJSON_ARRAY_INSERT(@j,'$[2][1]','y');
+---------------------------------------+
|JSON_ARRAY_INSERT(@j,'$[2][1]','y')|
+---------------------------------------+
|["a",{"b":[1,2]},[3,"y",4]]|
+---------------------------------------+
mysql>SELECTJSON_ARRAY_INSERT(@j,'$[0]','x','$[2][1]','y');
+----------------------------------------------------+
|JSON_ARRAY_INSERT(@j,'$[0]','x','$[2][1]','y')|
+----------------------------------------------------+
|["x","a",{"b":[1,2]},[3,4]]|
+----------------------------------------------------+

3.3.3JSON_INSERT/JSON_REPLACE/JSON_SET

JSON_INSERT(json_doc,path,val[,path,val]...)

在指定path下插入数据，如果path已存在，则忽略此val（不存在才插入）。

mysql>SET@j='{"a":1,"b":[2,3]}';
mysql>SELECTJSON_INSERT(@j,'$.a',10,'$.c','[true,false]');
+----------------------------------------------------+
|JSON_INSERT(@j,'$.a',10,'$.c','[true,false]')|
+----------------------------------------------------+
|{"a":1,"b":[2,3],"c":"[true,false]"}|
+----------------------------------------------------+

JSON_REPLACE(json_doc,path,val[,path,val]...)

替换指定路径的数据，如果某个路径不存在则略过（存在才替换）。如果有参数为NULL，则返回NULL。

mysql>SET@j='{"a":1,"b":[2,3]}';
mysql>SELECTJSON_REPLACE(@j,'$.a',10,'$.c','[true,false]');
+-----------------------------------------------------+
|JSON_REPLACE(@j,'$.a',10,'$.c','[true,false]')|
+-----------------------------------------------------+
|{"a":10,"b":[2,3]}|
+-----------------------------------------------------+

JSON_SET(json_doc,path,val[,path,val]...)

设置指定路径的数据（不管是否存在）。如果有参数为NULL，则返回NULL。

mysql>SET@j='{"a":1,"b":[2,3]}';
mysql>SELECTJSON_SET(@j,'$.a',10,'$.c','[true,false]');
+-------------------------------------------------+
|JSON_SET(@j,'$.a',10,'$.c','[true,false]')|
+-------------------------------------------------+
|{"a":10,"b":[2,3],"c":"[true,false]"}|
+-------------------------------------------------+
mysql>SELECTJSON_INSERT(@j,'$.a',10,'$.c','[true,false]');
+----------------------------------------------------+
|JSON_INSERT(@j,'$.a',10,'$.c','[true,false]')|
+----------------------------------------------------+
|{"a":1,"b":[2,3],"c":"[true,false]"}|
+----------------------------------------------------+
mysql>SELECTJSON_REPLACE(@j,'$.a',10,'$.c','[true,false]');
+-----------------------------------------------------+
|JSON_REPLACE(@j,'$.a',10,'$.c','[true,false]')|
+-----------------------------------------------------+
|{"a":10,"b":[2,3]}|
+-----------------------------------------------------+

3.3.4JSON_MERGE

JSON_MERGE(json_doc,json_doc[,json_doc]...)

merge多个json文档。规则如下：

如果都是jsonarray，则结果自动merge为一个jsonarray；
如果都是jsonobject，则结果自动merge为一个jsonobject；
如果有多种类型，则将非jsonarray的元素封装成jsonarray再按照规则一进行mege。

mysql>SELECTJSON_MERGE('[1,2]','[true,false]');
+---------------------------------------+
|JSON_MERGE('[1,2]','[true,false]')|
+---------------------------------------+
|[1,2,true,false]|
+---------------------------------------+
mysql>SELECTJSON_MERGE('{"name":"x"}','{"id":47}');
+-------------------------------------------+
|JSON_MERGE('{"name":"x"}','{"id":47}')|
+-------------------------------------------+
|{"id":47,"name":"x"}|
+-------------------------------------------+
mysql>SELECTJSON_MERGE('1','true');
+-------------------------+
|JSON_MERGE('1','true')|
+-------------------------+
|[1,true]|
+-------------------------+
mysql>SELECTJSON_MERGE('[1,2]','{"id":47}');
+------------------------------------+
|JSON_MERGE('[1,2]','{"id":47}')|
+------------------------------------+
|[1,2,{"id":47}]|
+------------------------------------+

3.3.5JSON_REMOVE

JSON_REMOVE(json_doc,path[,path]...)

移除指定路径的数据，如果某个路径不存在则略过此路径。如果有参数为NULL，则返回NULL。

mysql>SET@j='["a",["b","c"],"d"]';
mysql>SELECTJSON_REMOVE(@j,'$[1]');
+-------------------------+
|JSON_REMOVE(@j,'$[1]')|
+-------------------------+
|["a","d"]|
+-------------------------+

3.3.6JSON_UNQUOTE

JSON_UNQUOTE(val)

去掉val的引号。如果val为NULL，则返回NULL。

mysql>SET@j='"abc"';
mysql>SELECT@j,JSON_UNQUOTE(@j);
+-------+------------------+
|@j|JSON_UNQUOTE(@j)|
+-------+------------------+
|"abc"|abc|
+-------+------------------+
mysql>SET@j='[1,2,3]';
mysql>SELECT@j,JSON_UNQUOTE(@j);
+-----------+------------------+
|@j|JSON_UNQUOTE(@j)|
+-----------+------------------+
|[1,2,3]|[1,2,3]|
+-----------+------------------+

3.4JSON特性查询

3.4.1JSON_DEEPTH

JSON_DEPTH(json_doc)

获取json文档的深度。如果参数为NULL，则返回NULL。

空的jsonarray、jsonobject或标量的深度为1。

mysql>SELECTJSON_DEPTH('{}'),JSON_DEPTH('[]'),JSON_DEPTH('true');
+------------------+------------------+--------------------+
|JSON_DEPTH('{}')|JSON_DEPTH('[]')|JSON_DEPTH('true')|
+------------------+------------------+--------------------+
|1|1|1|
+------------------+------------------+--------------------+
mysql>SELECTJSON_DEPTH('[10,20]'),JSON_DEPTH('[[],{}]');
+------------------------+------------------------+
|JSON_DEPTH('[10,20]')|JSON_DEPTH('[[],{}]')|
+------------------------+------------------------+
|2|2|
+------------------------+------------------------+
mysql>SELECTJSON_DEPTH('[10,{"a":20}]');
+-------------------------------+
|JSON_DEPTH('[10,{"a":20}]')|
+-------------------------------+
|3|
+-------------------------------+

3.4.2JSON_LENGTH

JSON_LENGTH(json_doc[,path])

获取指定路径下的长度。如果参数为NULL，则返回NULL。

长度的计算规则：

标量的长度为1；
jsonarray的长度为元素的个数；
jsonobject的长度为key的个数。

mysql>SELECTJSON_LENGTH('[1,2,{"a":3}]');
+---------------------------------+
|JSON_LENGTH('[1,2,{"a":3}]')|
+---------------------------------+
|3|
+---------------------------------+
mysql>SELECTJSON_LENGTH('{"a":1,"b":{"c":30}}');
+-----------------------------------------+
|JSON_LENGTH('{"a":1,"b":{"c":30}}')|
+-----------------------------------------+
|2|
+-----------------------------------------+
mysql>SELECTJSON_LENGTH('{"a":1,"b":{"c":30}}','$.b');
+------------------------------------------------+
|JSON_LENGTH('{"a":1,"b":{"c":30}}','$.b')|
+------------------------------------------------+
|1|
+------------------------------------------------+

3.4.3JSON_TYPE

JSON_TYPE(json_val)

获取json文档的具体类型。如果参数为NULL，则返回NULL。

3.4.4JSON_VALID

JSON_VALID(val)

判断val是否为有效的json格式，是为1，不是为0。如果参数为NUL，则返回NULL。

mysql>SELECTJSON_VALID('{"a":1}');
+------------------------+
|JSON_VALID('{"a":1}')|
+------------------------+
|1|
+------------------------+
mysql>SELECTJSON_VALID('hello'),JSON_VALID('"hello"');
+---------------------+-----------------------+
|JSON_VALID('hello')|JSON_VALID('"hello"')|
+---------------------+-----------------------+
|0|1|
+---------------------+-----------------------+

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