云数据库 GAUSSDB-SELECT:语法格式

时间：2024-11-02 18:53:06

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 ]} [, ...] }
[ 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 ]
[ {FOR { UPDATE | NO KEY UPDATE | SHARE | KEY SHARE } [ OF table_name [, ...] ] [ NOWAIT | WAIT N ]} [...] ];

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 |  CS N} 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 [ 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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