MySQL 8.4 Reference Manual Including MySQL NDB Cluster 8.4
The functions in this section modify JSON values and return the result.
JSON_ARRAY_APPEND(
json_doc,
path,
val[,
path,
val] ...)
Appends values to the end of the indicated arrays within a
JSON document and returns the result. Returns
NULL if any argument is
NULL. An error occurs if the
json_doc argument is not a valid
JSON document or any path argument
is not a valid path expression or contains a
* or ** wildcard.
The path-value pairs are evaluated left to right. The document produced by evaluating one pair becomes the new value against which the next pair is evaluated.
If a path selects a scalar or object value, that value is autowrapped within an array and the new value is added to that array. Pairs for which the path does not identify any value in the JSON document are ignored.
mysql>SET @j = '["a", ["b", "c"], "d"]';mysql>SELECT JSON_ARRAY_APPEND(@j, '$[1]', 1);+----------------------------------+ | JSON_ARRAY_APPEND(@j, '$[1]', 1) | +----------------------------------+ | ["a", ["b", "c", 1], "d"] | +----------------------------------+ mysql>SELECT JSON_ARRAY_APPEND(@j, '$[0]', 2);+----------------------------------+ | JSON_ARRAY_APPEND(@j, '$[0]', 2) | +----------------------------------+ | [["a", 2], ["b", "c"], "d"] | +----------------------------------+ mysql>SELECT JSON_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>SELECT JSON_ARRAY_APPEND(@j, '$.b', 'x');+------------------------------------+ | JSON_ARRAY_APPEND(@j, '$.b', 'x') | +------------------------------------+ | {"a": 1, "b": [2, 3, "x"], "c": 4} | +------------------------------------+ mysql>SELECT JSON_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>SELECT JSON_ARRAY_APPEND(@j, '$', 'z');+---------------------------------+ | JSON_ARRAY_APPEND(@j, '$', 'z') | +---------------------------------+ | [{"a": 1}, "z"] | +---------------------------------+
JSON_ARRAY_INSERT(
json_doc,
path,
val[,
path,
val] ...)
Updates a JSON document, inserting into an array within the
document and returning the modified document. Returns
NULL if any argument is
NULL. An error occurs if the
json_doc argument is not a valid
JSON document or any path argument
is not a valid path expression or contains a
* or ** wildcard or does
not end with an array element identifier.
The path-value pairs are evaluated left to right. The document produced by evaluating one pair becomes the new value against which the next pair is evaluated.
Pairs for which the path does not identify any array in the JSON document are ignored. If a path identifies an array element, the corresponding value is inserted at that element position, shifting any following values to the right. If a path identifies an array position past the end of an array, the value is inserted at the end of the array.
mysql>SET @j = '["a", {"b": [1, 2]}, [3, 4]]';mysql>SELECT JSON_ARRAY_INSERT(@j, '$[1]', 'x');+------------------------------------+ | JSON_ARRAY_INSERT(@j, '$[1]', 'x') | +------------------------------------+ | ["a", "x", {"b": [1, 2]}, [3, 4]] | +------------------------------------+ mysql>SELECT JSON_ARRAY_INSERT(@j, '$[100]', 'x');+--------------------------------------+ | JSON_ARRAY_INSERT(@j, '$[100]', 'x') | +--------------------------------------+ | ["a", {"b": [1, 2]}, [3, 4], "x"] | +--------------------------------------+ mysql>SELECT JSON_ARRAY_INSERT(@j, '$[1].b[0]', 'x');+-----------------------------------------+ | JSON_ARRAY_INSERT(@j, '$[1].b[0]', 'x') | +-----------------------------------------+ | ["a", {"b": ["x", 1, 2]}, [3, 4]] | +-----------------------------------------+ mysql>SELECT JSON_ARRAY_INSERT(@j, '$[2][1]', 'y');+---------------------------------------+ | JSON_ARRAY_INSERT(@j, '$[2][1]', 'y') | +---------------------------------------+ | ["a", {"b": [1, 2]}, [3, "y", 4]] | +---------------------------------------+ mysql>SELECT JSON_ARRAY_INSERT(@j, '$[0]', 'x', '$[2][1]', 'y');+----------------------------------------------------+ | JSON_ARRAY_INSERT(@j, '$[0]', 'x', '$[2][1]', 'y') | +----------------------------------------------------+ | ["x", "a", {"b": [1, 2]}, [3, 4]] | +----------------------------------------------------+
Earlier modifications affect the positions of the following
elements in the array, so subsequent paths in the same
JSON_ARRAY_INSERT() call should
take this into account. In the final example, the second path
inserts nothing because the path no longer matches anything
after the first insert.
JSON_INSERT(
json_doc,
path,
val[,
path,
val] ...)
Inserts data into a JSON document and returns the result.
Returns NULL if any argument is
NULL. An error occurs if the
json_doc argument is not a valid
JSON document or any path argument
is not a valid path expression or contains a
* or ** wildcard.
The path-value pairs are evaluated left to right. The document produced by evaluating one pair becomes the new value against which the next pair is evaluated.
A path-value pair for an existing path in the document is ignored and does not overwrite the existing document value. A path-value pair for a nonexisting path in the document adds the value to the document if the path identifies one of these types of values:
A member not present in an existing object. The member is added to the object and associated with the new value.
A position past the end of an existing array. The array is extended with the new value. If the existing value is not an array, it is autowrapped as an array, then extended with the new value.
Otherwise, a path-value pair for a nonexisting path in the document is ignored and has no effect.
For a comparison of
JSON_INSERT(),
JSON_REPLACE(), and
JSON_SET(), see the discussion
of JSON_SET().
mysql>SET @j = '{ "a": 1, "b": [2, 3]}';mysql>SELECT JSON_INSERT(@j, '$.a', 10, '$.c', '[true, false]');+----------------------------------------------------+ | JSON_INSERT(@j, '$.a', 10, '$.c', '[true, false]') | +----------------------------------------------------+ | {"a": 1, "b": [2, 3], "c": "[true, false]"} | +----------------------------------------------------+
The third and final value listed in the result is a quoted string and not an array like the second one (which is not quoted in the output); no casting of values to the JSON type is performed. To insert the array as an array, you must perform such casts explicitly, as shown here:
mysql> SELECT JSON_INSERT(@j, '$.a', 10, '$.c', CAST('[true, false]' AS JSON));
+------------------------------------------------------------------+
| JSON_INSERT(@j, '$.a', 10, '$.c', CAST('[true, false]' AS JSON)) |
+------------------------------------------------------------------+
| {"a": 1, "b": [2, 3], "c": [true, false]} |
+------------------------------------------------------------------+
1 row in set (0.00 sec)
JSON_MERGE(
json_doc,
json_doc[,
json_doc] ...)
Deprecated synonym for
JSON_MERGE_PRESERVE().
JSON_MERGE_PATCH(
json_doc,
json_doc[,
json_doc] ...)
Performs an RFC 7396 compliant merge of two or more JSON documents and returns the merged result, without preserving members having duplicate keys. Raises an error if at least one of the documents passed as arguments to this function is not valid.
For an explanation and example of the differences between
this function and JSON_MERGE_PRESERVE(),
see
JSON_MERGE_PATCH() compared with JSON_MERGE_PRESERVE().
JSON_MERGE_PATCH() performs a merge as
follows:
If the first argument is not an object, the result of the merge is the same as if an empty object had been merged with the second argument.
If the second argument is not an object, the result of the merge is the second argument.
If both arguments are objects, the result of the merge is an object with the following members:
All members of the first object which do not have a corresponding member with the same key in the second object.
All members of the second object which do not have a
corresponding key in the first object, and whose value
is not the JSON null literal.
All members with a key that exists in both the first
and the second object, and whose value in the second
object is not the JSON null
literal. The values of these members are the results
of recursively merging the value in the first object
with the value in the second object.
For additional information, see Normalization, Merging, and Autowrapping of JSON Values.
mysql>SELECT JSON_MERGE_PATCH('[1, 2]', '[true, false]');+---------------------------------------------+ | JSON_MERGE_PATCH('[1, 2]', '[true, false]') | +---------------------------------------------+ | [true, false] | +---------------------------------------------+ mysql>SELECT JSON_MERGE_PATCH('{"name": "x"}', '{"id": 47}');+-------------------------------------------------+ | JSON_MERGE_PATCH('{"name": "x"}', '{"id": 47}') | +-------------------------------------------------+ | {"id": 47, "name": "x"} | +-------------------------------------------------+ mysql>SELECT JSON_MERGE_PATCH('1', 'true');+-------------------------------+ | JSON_MERGE_PATCH('1', 'true') | +-------------------------------+ | true | +-------------------------------+ mysql>SELECT JSON_MERGE_PATCH('[1, 2]', '{"id": 47}');+------------------------------------------+ | JSON_MERGE_PATCH('[1, 2]', '{"id": 47}') | +------------------------------------------+ | {"id": 47} | +------------------------------------------+ mysql>SELECT JSON_MERGE_PATCH('{ "a": 1, "b":2 }',>'{ "a": 3, "c":4 }');+-----------------------------------------------------------+ | JSON_MERGE_PATCH('{ "a": 1, "b":2 }','{ "a": 3, "c":4 }') | +-----------------------------------------------------------+ | {"a": 3, "b": 2, "c": 4} | +-----------------------------------------------------------+ mysql>SELECT JSON_MERGE_PATCH('{ "a": 1, "b":2 }','{ "a": 3, "c":4 }',>'{ "a": 5, "d":6 }');+-------------------------------------------------------------------------------+ | JSON_MERGE_PATCH('{ "a": 1, "b":2 }','{ "a": 3, "c":4 }','{ "a": 5, "d":6 }') | +-------------------------------------------------------------------------------+ | {"a": 5, "b": 2, "c": 4, "d": 6} | +-------------------------------------------------------------------------------+
You can use this function to remove a member by specifying
null as the value of the same member in the
second argument, as shown here:
mysql> SELECT JSON_MERGE_PATCH('{"a":1, "b":2}', '{"b":null}');
+--------------------------------------------------+
| JSON_MERGE_PATCH('{"a":1, "b":2}', '{"b":null}') |
+--------------------------------------------------+
| {"a": 1} |
+--------------------------------------------------+
This example shows that the function operates in a recursive fashion; that is, values of members are not limited to scalars, but rather can themselves be JSON documents:
mysql> SELECT JSON_MERGE_PATCH('{"a":{"x":1}}', '{"a":{"y":2}}');
+----------------------------------------------------+
| JSON_MERGE_PATCH('{"a":{"x":1}}', '{"a":{"y":2}}') |
+----------------------------------------------------+
| {"a": {"x": 1, "y": 2}} |
+----------------------------------------------------+
JSON_MERGE_PATCH() compared with JSON_MERGE_PRESERVE().
The behavior of JSON_MERGE_PATCH() is the
same as that of
JSON_MERGE_PRESERVE(), with
the following two exceptions:
JSON_MERGE_PATCH() removes any member
in the first object with a matching key in the second
object, provided that the value associated with the key in
the second object is not JSON null.
If the second object has a member with a key matching a
member in the first object,
JSON_MERGE_PATCH()
replaces the value in the first
object with the value in the second object, whereas
JSON_MERGE_PRESERVE()
appends the second value to the first
value.
This example compares the results of merging the same 3 JSON
objects, each having a matching key "a",
with each of these two functions:
mysql>SET @x = '{ "a": 1, "b": 2 }',>@y = '{ "a": 3, "c": 4 }',>@z = '{ "a": 5, "d": 6 }';mysql>SELECT JSON_MERGE_PATCH(@x, @y, @z) AS Patch,->JSON_MERGE_PRESERVE(@x, @y, @z) AS Preserve\G*************************** 1. row *************************** Patch: {"a": 5, "b": 2, "c": 4, "d": 6} Preserve: {"a": [1, 3, 5], "b": 2, "c": 4, "d": 6}
JSON_MERGE_PRESERVE(
json_doc,
json_doc[,
json_doc] ...)
Merges two or more JSON documents and returns the merged
result. Returns NULL if any argument is
NULL. An error occurs if any argument is
not a valid JSON document.
Merging takes place according to the following rules. For additional information, see Normalization, Merging, and Autowrapping of JSON Values.
Adjacent arrays are merged to a single array.
Adjacent objects are merged to a single object.
A scalar value is autowrapped as an array and merged as an array.
An adjacent array and object are merged by autowrapping the object as an array and merging the two arrays.
mysql>SELECT JSON_MERGE_PRESERVE('[1, 2]', '[true, false]');+------------------------------------------------+ | JSON_MERGE_PRESERVE('[1, 2]', '[true, false]') | +------------------------------------------------+ | [1, 2, true, false] | +------------------------------------------------+ mysql>SELECT JSON_MERGE_PRESERVE('{"name": "x"}', '{"id": 47}');+----------------------------------------------------+ | JSON_MERGE_PRESERVE('{"name": "x"}', '{"id": 47}') | +----------------------------------------------------+ | {"id": 47, "name": "x"} | +----------------------------------------------------+ mysql>SELECT JSON_MERGE_PRESERVE('1', 'true');+----------------------------------+ | JSON_MERGE_PRESERVE('1', 'true') | +----------------------------------+ | [1, true] | +----------------------------------+ mysql>SELECT JSON_MERGE_PRESERVE('[1, 2]', '{"id": 47}');+---------------------------------------------+ | JSON_MERGE_PRESERVE('[1, 2]', '{"id": 47}') | +---------------------------------------------+ | [1, 2, {"id": 47}] | +---------------------------------------------+ mysql>SELECT JSON_MERGE_PRESERVE('{ "a": 1, "b": 2 }',>'{ "a": 3, "c": 4 }');+--------------------------------------------------------------+ | JSON_MERGE_PRESERVE('{ "a": 1, "b": 2 }','{ "a": 3, "c":4 }') | +--------------------------------------------------------------+ | {"a": [1, 3], "b": 2, "c": 4} | +--------------------------------------------------------------+ mysql>SELECT JSON_MERGE_PRESERVE('{ "a": 1, "b": 2 }','{ "a": 3, "c": 4 }',>'{ "a": 5, "d": 6 }');+----------------------------------------------------------------------------------+ | JSON_MERGE_PRESERVE('{ "a": 1, "b": 2 }','{ "a": 3, "c": 4 }','{ "a": 5, "d": 6 }') | +----------------------------------------------------------------------------------+ | {"a": [1, 3, 5], "b": 2, "c": 4, "d": 6} | +----------------------------------------------------------------------------------+
This function is similar to but differs from
JSON_MERGE_PATCH() in
significant respects; see
JSON_MERGE_PATCH() compared with JSON_MERGE_PRESERVE(),
for more information.
JSON_REMOVE(
json_doc,
path[,
path] ...)
Removes data from a JSON document and returns the result.
Returns NULL if any argument is
NULL. An error occurs if the
json_doc argument is not a valid
JSON document or any path argument
is not a valid path expression or is $ or
contains a * or **
wildcard.
The path arguments are evaluated
left to right. The document produced by evaluating one path
becomes the new value against which the next path is
evaluated.
It is not an error if the element to be removed does not exist in the document; in that case, the path does not affect the document.
mysql>SET @j = '["a", ["b", "c"], "d"]';mysql>SELECT JSON_REMOVE(@j, '$[1]');+-------------------------+ | JSON_REMOVE(@j, '$[1]') | +-------------------------+ | ["a", "d"] | +-------------------------+
JSON_REPLACE(
json_doc,
path,
val[,
path,
val] ...)
Replaces existing values in a JSON document and returns the
result. Returns NULL if
json_doc or any
path argument is
NULL. An error occurs if the
json_doc argument is not a valid
JSON document or any path argument
is not a valid path expression or contains a
* or ** wildcard.
The path-value pairs are evaluated left to right. The document produced by evaluating one pair becomes the new value against which the next pair is evaluated.
A path-value pair for an existing path in the document overwrites the existing document value with the new value. A path-value pair for a nonexisting path in the document is ignored and has no effect.
The optimizer can perform a partial, in-place update of a
JSON column instead of removing the old
document and writing the new document in its entirety to the
column. This optimization can be performed for an update
statement that uses the
JSON_REPLACE() function and
meets the conditions outlined in
Partial Updates of JSON Values.
For a comparison of
JSON_INSERT(),
JSON_REPLACE(), and
JSON_SET(), see the discussion
of JSON_SET().
mysql>SET @j = '{ "a": 1, "b": [2, 3]}';mysql>SELECT JSON_REPLACE(@j, '$.a', 10, '$.c', '[true, false]');+-----------------------------------------------------+ | JSON_REPLACE(@j, '$.a', 10, '$.c', '[true, false]') | +-----------------------------------------------------+ | {"a": 10, "b": [2, 3]} | +-----------------------------------------------------+ mysql>SELECT JSON_REPLACE(NULL, '$.a', 10, '$.c', '[true, false]');+-------------------------------------------------------+ | JSON_REPLACE(NULL, '$.a', 10, '$.c', '[true, false]') | +-------------------------------------------------------+ | NULL | +-------------------------------------------------------+ mysql>SELECT JSON_REPLACE(@j, NULL, 10, '$.c', '[true, false]');+----------------------------------------------------+ | JSON_REPLACE(@j, NULL, 10, '$.c', '[true, false]') | +----------------------------------------------------+ | NULL | +----------------------------------------------------+ mysql>SELECT JSON_REPLACE(@j, '$.a', NULL, '$.c', '[true, false]');+-------------------------------------------------------+ | JSON_REPLACE(@j, '$.a', NULL, '$.c', '[true, false]') | +-------------------------------------------------------+ | {"a": null, "b": [2, 3]} | +-------------------------------------------------------+
JSON_SET(
json_doc,
path,
val[,
path,
val] ...)
Inserts or updates data in a JSON document and returns the
result. Returns NULL if
json_doc or
path is NULL, or
if path, when given, does not
locate an object. Otherwise, an error occurs if the
json_doc argument is not a valid
JSON document or any path argument
is not a valid path expression or contains a
* or ** wildcard.
The path-value pairs are evaluated left to right. The document produced by evaluating one pair becomes the new value against which the next pair is evaluated.
A path-value pair for an existing path in the document overwrites the existing document value with the new value. A path-value pair for a nonexisting path in the document adds the value to the document if the path identifies one of these types of values:
A member not present in an existing object. The member is added to the object and associated with the new value.
A position past the end of an existing array. The array is extended with the new value. If the existing value is not an array, it is autowrapped as an array, then extended with the new value.
Otherwise, a path-value pair for a nonexisting path in the document is ignored and has no effect.
The optimizer can perform a partial, in-place update of a
JSON column instead of removing the old
document and writing the new document in its entirety to the
column. This optimization can be performed for an update
statement that uses the
JSON_SET() function and meets
the conditions outlined in
Partial Updates of JSON Values.
The JSON_SET(),
JSON_INSERT(), and
JSON_REPLACE() functions are
related:
JSON_SET() replaces
existing values and adds nonexisting values.
JSON_INSERT() inserts
values without replacing existing values.
JSON_REPLACE() replaces
only existing values.
The following examples illustrate these differences, using one
path that does exist in the document ($.a)
and another that does not exist ($.c):
mysql>SET @j = '{ "a": 1, "b": [2, 3]}';mysql>SELECT JSON_SET(@j, '$.a', 10, '$.c', '[true, false]');+-------------------------------------------------+ | JSON_SET(@j, '$.a', 10, '$.c', '[true, false]') | +-------------------------------------------------+ | {"a": 10, "b": [2, 3], "c": "[true, false]"} | +-------------------------------------------------+ mysql>SELECT JSON_INSERT(@j, '$.a', 10, '$.c', '[true, false]');+----------------------------------------------------+ | JSON_INSERT(@j, '$.a', 10, '$.c', '[true, false]') | +----------------------------------------------------+ | {"a": 1, "b": [2, 3], "c": "[true, false]"} | +----------------------------------------------------+ mysql>SELECT JSON_REPLACE(@j, '$.a', 10, '$.c', '[true, false]');+-----------------------------------------------------+ | JSON_REPLACE(@j, '$.a', 10, '$.c', '[true, false]') | +-----------------------------------------------------+ | {"a": 10, "b": [2, 3]} | +-----------------------------------------------------+
Unquotes JSON value and returns the result as a
utf8mb4 string. Returns
NULL if the argument is
NULL. An error occurs if the value starts
and ends with double quotes but is not a valid JSON string
literal.
Within a string, certain sequences have special meaning unless
the NO_BACKSLASH_ESCAPES SQL
mode is enabled. Each of these sequences begins with a
backslash (\), known as the
escape character. MySQL recognizes the
escape sequences shown in
Table 14.23, “JSON_UNQUOTE() Special Character Escape Sequences”. For
all other escape sequences, backslash is ignored. That is, the
escaped character is interpreted as if it was not escaped. For
example, \x is just x.
These sequences are case-sensitive. For example,
\b is interpreted as a backspace, but
\B is interpreted as B.
Two simple examples of the use of this function are shown here:
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] | +-----------+------------------+
The following set of examples shows how
JSON_UNQUOTE handles escapes with
NO_BACKSLASH_ESCAPES
disabled and enabled:
mysql>SELECT @@sql_mode;+------------+ | @@sql_mode | +------------+ | | +------------+ mysql>SELECT JSON_UNQUOTE('"\\t\\u0032"');+------------------------------+ | JSON_UNQUOTE('"\\t\\u0032"') | +------------------------------+ | 2 | +------------------------------+ mysql>SET @@sql_mode = 'NO_BACKSLASH_ESCAPES';mysql>SELECT JSON_UNQUOTE('"\\t\\u0032"');+------------------------------+ | JSON_UNQUOTE('"\\t\\u0032"') | +------------------------------+ | \t\u0032 | +------------------------------+ mysql>SELECT JSON_UNQUOTE('"\t\u0032"');+----------------------------+ | JSON_UNQUOTE('"\t\u0032"') | +----------------------------+ | 2 | +----------------------------+