Many of the functions described in previous sections require a path expression in order to identify a specific element in a JSON document. A path consists of the path's scope followed by one or more path legs. For paths used in MySQL JSON functions, the scope is always the document being searched or otherwise operated on, represented by a leading $ character. Path legs are separated by period characters (.). Cells in arrays are represented by [N], where N is a non-negative integer. Names of keys must be double-quoted strings or valid ECMAScript identifiers (see http://www.ecma-international.org/ecma-262/5.1/#sec-7.6). Path expressions, like JSON text, should be encoded using the ascii, utf8, or utf8mb4 character sets. Other character encodings are implicitly coerced to utf8mb4. The complete syntax is shown here:

pathExpression:
    scope[(pathLeg)*]

pathLeg:
    member | arrayLocation | doubleAsterisk

member:
    period ( keyName | asterisk )

arrayLocation:
    leftBracket ( nonNegativeInteger | asterisk ) rightBracket

keyName:
    ESIdentifier | doubleQuotedString

doubleAsterisk:
    '**'

period:
    '.'

asterisk:
    '*'

leftBracket:
    '['

rightBracket:
    ']'

As noted previously, in MySQL, the scope of the path is always the document being operated on, represented as $. You can use '$' as a synonynm for the document in JSON path expressions.

The wildcard * and ** tokens are used as follows:

For path syntax examples, see the descriptions of the various JSON fuinctions that take paths as arguments, such as JSON_CONTAINS_PATH(), JSON_SET(), and JSON_REPLACE(). For examples which include the use of the * and ** wildcards, see the description of the JSON_SEARCH() function.