- StarRocks
- Introduction to StarRocks
- Quick Start
- Table Design
- Data Loading
- Concepts
- Overview of data loading
- Load data from a local file system or a streaming data source using HTTP PUT
- Load data from HDFS or cloud storage
- Continuously load data from Apache Kafka®
- Bulk load using Apache Spark™
- Load data using INSERT
- Synchronize data from MySQL in real time
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- Change data through loading
- Transform data at loading
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- Query Acceleration
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- ADD SQLBLACKLIST
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- Auxiliary Commands
- Data Types
- Function Reference
- Java UDFs
- Window functions
- Aggregate Functions
- Array Functions
- Bit Functions
- Bitmap Functions
- base64_to_bitmap
- bitmap_agg
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- bitmap_count
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- bitmap_empty
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- Conditional Functions
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- Date Functions
- add_months
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- date
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- date_sub, subdate
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- day
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- days_sub
- from_days
- from_unixtime
- hour
- hours_add
- hours_diff
- hours_sub
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- microseconds_sub
- minute
- minutes_add
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- minutes_sub
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- monthname
- months_add
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- months_sub
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- seconds_add
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- seconds_sub
- str_to_date
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- time_slice
- time_to_sec
- timediff
- timestamp
- timestampadd
- timestampdiff
- to_date
- to_days
- unix_timestamp
- utc_timestamp
- week
- weekofyear
- weeks_add
- weeks_diff
- weeks_sub
- year
- years_add
- years_diff
- years_sub
- Geographic Functions
- JSON Functions
- Overview of JSON functions and operators
- JSON operators
- JSON constructor functions
- JSON query and processing functions
- Math Functions
- String Functions
- Pattern Matching Functions
- Percentile Functions
- Scalar Functions
- Utility Functions
- cast function
- hash function
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- SQL Reference
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- Use the debuginfo file for debugging
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Arrow function
Description
Queries an element that can be located by the json_path
expression in a JSON object and returns a JSON value. The arrow function ->
is more compact and easier to use than the json_query function.
Syntax
json_object_expr -> json_path
Parameters
json_object_expr
: the expression that represents the JSON object. The object can be a JSON column, or a JSON object that is produced by a JSON constructor function such as PARSE_JSON.json_path
: the expression that represents the path to an element in the JSON object. The value of this parameter is a string. For information about the JSON path syntax that is supported by StarRocks, see Overview of JSON functions and operators.
Return value
Returns a JSON value.
If the element does not exist, the arrow function returns an SQL value of
NULL
.
Examples
Example 1: Query an element that can be located by the '$.a.b'
expression in the specified JSON object.
mysql> SELECT parse_json('{"a": {"b": 1}}') -> '$.a.b';
-> 1
Example 2: Use nested arrow functions to query an element. The arrow function in which another arrow function is nested queries an element based on the result that is returned by the nested arrow function.
In this example, the root element $ is omitted from the
json_path
expression.
mysql> SELECT parse_json('{"a": {"b": 1}}')->'a'->'b';
-> 1
Example 3: Query an element that can be located by the 'a'
expression in the specified JSON object.
In this example, the root element $ is omitted from the
json_path
expression.
mysql> SELECT parse_json('{"a": "b"}') -> 'a';
-> "b"