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DocumentationTDSQL-C for MySQLOperation GuideRead-Only Analysis EngineExecuting QueriesSELECT Statement Instructions
SELECT Statement Instructions
Last updated: 2024-12-17 16:40:11
This document introduces the query statements supported in the read-only analysis engine and provides related descriptions.
Object Permission Description
In the read-only analysis engine, only objects fully loaded into the analysis engine support data queries. To query data, you should have the SELECT permissions for the corresponding data table. If you have no permissions, you can obtain the object permissions through TDSQL-C for MySQL account management. For the operation, see Modifying Account Permissions.
SELECT Statement
The read-only analysis engine mainly supports data queries using SELECT statements.
SELECT [ALL | DISTINCT | DISTINCTROW ] select_expr [, select_expr] ... [FROM table_references [WHERE where_condition] [GROUP BY {col_name | expr | position}] [HAVING where_condition] [WINDOW window_name AS (window_spec) [, window_name AS (window_spec)] ...] [ORDER BY {col_name | expr | position} [ASC | DESC]] [LIMIT {[offset,] row_count | row_count OFFSET offset}]
The above SELECT statement block includes SELECT statements supported in the read-only analysis engine. The following describes statement units not supported in the read-only analysis engine in a complete SELECT statement segment of MySQL:
HIGH_PRIORITY indicates setting the priority for executing SELECT statements. This will not take effect in the read-only analysis engine, but if this keyword is contained in an SQL statement, it will not affect the execution result.
STRAIGHT_JOIN indicates forcing the optimizer to join tables in the order as they are listed in the clause. However, in the read-only analysis engine, the execution plan is selected entirely based on the columnar execution optimizer of the engine, so this keyword will not take effect.
The query options SQL_SMALL_RESULT, SQL_BIG_RESULT, SQL_BUFFER_RESULT, SQL_NO_CACHE, and SQL_CALC_FOUND_ROWS will also not take effect in the read-only analysis engine, but will not affect the execution of query statements.
The PARTITION partition_list clause is not supported in the read-only analysis engine, and this option will cause queries to fail.
The WITH ROLLUP syntax is not supported. If this keyword is contained in an SQL statement, an error will be reported during query execution.
The FOR UPDATE and LOCK IN SHARE MODE clauses are not supported. If such clauses are contained in an SQL statement to be executed, they will not take effect and the SQL statement will be executed normally.
The INTO option is not supported. If this keyword is contained in a statement, an error will be reported during execution.
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