14.17.2 创建 JSON 值的函数
The functions listed in this section compose JSON values from component elements.
-
Evaluates a (possibly empty) list of values and returns a JSON array containing those values.
mysql> SELECT JSON_ARRAY(1, "abc", NULL, TRUE, CURTIME()); +---------------------------------------------+ | JSON_ARRAY(1, "abc", NULL, TRUE, CURTIME()) | +---------------------------------------------+ | [1, "abc", null, true, "11:30:24.000000"] | +---------------------------------------------+
-
JSON_OBJECT([
key
,val
[,key
,val
] ...])Evaluates a (possibly empty) list of key-value pairs and returns a JSON object containing those pairs. An error occurs if any key name is
NULL
or the number of arguments is odd.mysql> SELECT JSON_OBJECT('id', 87, 'name', 'carrot'); +-----------------------------------------+ | JSON_OBJECT('id', 87, 'name', 'carrot') | +-----------------------------------------+ | {"id": 87, "name": "carrot"} | +-----------------------------------------+
-
Quotes a string as a JSON value by wrapping it with double quote characters and escaping interior quote and other characters, then returning the result as a
utf8mb4
string. ReturnsNULL
if the argument isNULL
.This function is typically used to produce a valid JSON string literal for inclusion within a JSON document.
Certain special characters are escaped with backslashes per the escape sequences shown in Table 14.23, “JSON_UNQUOTE() Special Character Escape Sequences”.
mysql> SELECT JSON_QUOTE('null'), JSON_QUOTE('"null"'); +--------------------+----------------------+ | JSON_QUOTE('null') | JSON_QUOTE('"null"') | +--------------------+----------------------+ | "null" | "\"null\"" | +--------------------+----------------------+ mysql> SELECT JSON_QUOTE('[1, 2, 3]'); +-------------------------+ | JSON_QUOTE('[1, 2, 3]') | +-------------------------+ | "[1, 2, 3]" | +-------------------------+
You can also obtain JSON values by casting values of other types to the JSON
type using CAST(
; see Converting between JSON and non-JSON values, for more information.value
AS JSON)
Two aggregate functions generating JSON values are available. JSON_ARRAYAGG()
returns a result set as a single JSON array, and JSON_OBJECTAGG()
returns a result set as a single JSON object. For more information, see Section 14.19, “Aggregate Functions”.