云数据库 GaussDB-SELECT:语法格式

时间：2023-11-01 16:18:33

云数据库 GaussDB

语法格式

查询数据

[ WITH [ RECURSIVE ] with_query [, ...] ]SELECT [/*+ plan_hint */] [ ALL | DISTINCT [ ON ( expression [, ...] ) ] ]{ * | {expression [ [ AS ] output_name ]} [, ...] }[ into_option ][ FROM from_item [, ...] ][ WHERE condition ][ [ START WITH condition ] CONNECT BY [NOCYCLE] condition [ ORDER SIBLINGS BY expression ] ][ GROUP BY grouping_element [, ...] ][ HAVING condition [, ...] ][ WINDOW {window_name AS ( window_definition )} [, ...] ][ { UNION | INTERSECT | EXCEPT | MINUS } [ ALL | DISTINCT ] select ][ ORDER BY {expression [ [ ASC | DESC | USING operator ] | nlssort_expression_clause ] [ NULLS { FIRST | LAST } ]} [, ...] ][ LIMIT { [offset,] count | ALL } ][ OFFSET start [ ROW | ROWS ] ][ FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY ][ into_option ][ {FOR { UPDATE | NO KEY UPDATE | SHARE | KEY SHARE } [ OF table_name [, ...] ] [ NOWAIT | WAIT N ]} [...] ][into_option];

condition和expression中可以使用targetlist中表达式的别名。

只能同一层引用。
只能引用targetlist中的别名。
只能是后面的表达式引用前面的表达式。
不能包含volatile函数。
不能包含Window function函数。
不支持在join on条件中引用别名。
targetlist中有多个要应用的别名则报错。

其中子查询with_query为：

with_query_name [ ( column_name [, ...] ) ]    AS [ [ NOT ] MATERIALIZED ] ( {select | values | insert | update | delete} )

其中into字句为：

into_option: {        INTO var_name [, var_name] ...| INTO OUTFILE 'file_name'[CHARACTER SET charset_name]export_options| INTO DUMPFILE 'file_name'}export_options: {    [FIELDS [TERMINATED BY 'string'] [[OPTIONALLY] ENCLOSED BY 'char'] [ESCAPED BY 'char' ]    ]    [LINES [STARTING BY 'string'] [TERMINATED BY 'string']    ]}

其中指定查询源from_item为：

{[ ONLY ] table_name [ * ] [ partition_clause ] [ [ AS ] alias [ ( column_alias [, ...] ) ] ][ TABLESAMPLE sampling_method ( argument [, ...] ) [ REPEATABLE ( seed ) ] ][ TIMECAPSULE {TIMESTAMP | CSN} expression ]|( select ) [ AS ] alias [ ( column_alias [, ...] ) ]|with_query_name [ [ AS ] alias [ ( column_alias [, ...] ) ] ]|function_name ( [ argument [, ...] ] ) [ AS ] alias [ ( column_alias [, ...] | column_definition [, ...] ) ]|function_name ( [ argument [, ...] ] ) AS ( column_definition [, ...] )|from_item unpivot_clause|from_item pivot_clause|from_item [ NATURAL ] join_type from_item [ ON join_condition | USING ( join_column [, ...] ) ]}

其中group子句为：

( )| expression| ( expression [, ...] )| ROLLUP ( { expression | ( expression [, ...] ) } [, ...] )| CUBE ( { expression | ( expression [, ...] ) } [, ...] )| GROUPING SETS ( grouping_element [, ...] )

其中指定分区partition_clause为：

PARTITION { ( partition_name ) | FOR (  partition_value [, ...] ) } |SUBPARTITION { ( subpartition_name ) | FOR (  subpartition_value [, ...] )}

指定分区只适合分区表。

其中设置排序方式nlssort_expression_clause为：

NLSSORT ( column_name, ' NLS_SORT = { SCHINESE_PINYIN_M | generic_m_ci } ' )其中，第二个参数可选generic_m_ci，仅支持纯英文不区分大小写排序。

简化版查询语法，功能相当于select * from table_name。
```
TABLE { ONLY {(table_name)| table_name} | table_name [ * ]};
```

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语法格式

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