Extract value without quotation mark from MySQL JSON data type

Question

I have started using the JSON data type in mysql 5.7. Is there a way to extract a value without the quotation marks? For instance when setting up a virtual index.

Example:

mysql> INSERT INTO test (data) VALUES ('{"type": "user" , 
"content" : { "username": "jdoe", "firstname" : "John", "lastname" : "Doe" } }');

mysql> SELECT json_extract(data,'$.type') FROM test;
+-----------------------------+
| json_extract(data,'$.type') |
+-----------------------------+
| "user"                      |
+-----------------------------+

How to get

+-----------------------------+
| json_extract(data,'$.type') |
+-----------------------------+
| user                        |
+-----------------------------+

?

Answer 1

You can use ->> operator to extract unquoted data, simply!

SELECT JSONCOL->>'$.PATH' FROM tableName

Two other ways:

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

Note: Three different ways yield to the same command, as EXPLAIN explains:

As with ->, the ->> operator is always expanded in the output of EXPLAIN, as the following example demonstrates:

EXPLAIN SELECT c->>'$.name' AS name FROM jemp WHERE g > 2 ;
SHOW WARNINGS ;
*************************** 1. row ***************************
Level: Note
Code: 1003
Message: /* select#1 */ select
json_unquote(json_extract(`jtest`.`jemp`.`c`,'$.name')) AS `name` from
`jtest`.`jemp` where (`jtest`.`jemp`.`g` > 2)
1 row in set (0.00 sec)

read more on MySQL Reference Manual https://dev.mysql.com/doc/refman/5.7/en/json-search-functions.html#operator_json-inline-path

Note: The ->> operator was added in MySQL 5.7.13

Answer 2

You can use JSON_UNQUOTE() method:

SELECT JSON_UNQUOTE(json_extract(data,'$.type')) FROM test;

This method will deal with internal quotes, for instance:

SET @t1 := '{"a": "Hello \\\"Name\\\""}';
SET @j := CAST(@t1 AS JSON);
SET @tOut := JSON_EXTRACT(@j, '$.a');
SELECT @t1, @j, @tOut, JSON_UNQUOTE(@tOut), TRIM(BOTH '"' FROM @tOut);

will give:

@t1     : {"a": "Hello \"Name\""}
@j      : {"a": "Hello \"Name\""}
@tOut   : "Hello \"Name\""
unquote : Hello "Name"
trim    : Hello \"Name\

I believe that the unquote is better in almost all circumstances.

Answer 3

MySQL 8.0.21 supports JSON_VALUE function

Extracts a value from a JSON document at the path given in the specified document, and returns the extracted value, optionally converting it to a desired type. The complete syntax is shown here:

JSON_VALUE(json_doc, path [RETURNING type] [on_empty] [on_error])
on_empty:
       {NULL | ERROR | DEFAULT value} ON EMPTY
on_error:
       {NULL | ERROR | DEFAULT value} ON ERROR

If not specified by a RETURNING clause, the JSON_VALUE() function's return type is VARCHAR(512)

db<>fiddle demo

SELECT json_value(data,'$.type')
FROM test;
-- user