openGauss高级特性：附录：SQL语法（19）

TRUNCATE

清理表数据，TRUNCATE快速地从表中删除所有行。

TRUNCATE [ TABLE ] [ ONLY ] {table_name [ * ]} [, ... ]
    [ CONTINUE IDENTITY ] [ CASCADE | RESTRICT ];
ALTER TABLE [ IF EXISTS  ] { [ ONLY  ] table_name  | table_name *  | ONLY ( table_name )  }
    TRUNCATE PARTITION { partition_name  | FOR (  partition_value  [, ...] )  } ;

UPDATE

更新表中的数据。UPDATE修改满足条件的所有行中指定的字段值，WHERE子句声明条件，SET子句指定的字段会被修改，没有出现的字段则保持它们的原值。

UPDATE [/*+ plan_hint */] [ ONLY ] table_name [ * ] [ [ AS ] alias ]
    SET {column_name = { expression | DEFAULT } |
          ( column_name [, ...] ) = {( { expression | DEFAULT } [, ...] ) |sub_query }
          }[, ...]
    [ FROM from_list] [ WHERE condition ]
    [ RETURNING {* | {output_expression [ [ AS ] output_name ]} [, ...] }];

VACUUM

VACUUM回收表或B-Tree索引中已经删除的行所占据的存储空间。在一般的数据库操作里，那些已经DELETE的行并没有从它们所属的表中物理删除；在完成VACUUM之前它们仍然存在。因此有必要周期地运行VACUUM，特别是在经常更新的表上。

VACUUM [ ( { FULL | FREEZE | VERBOSE | {ANALYZE | ANALYSE }} [,...] ) ]
    [ table_name [ (column_name [, ...] ) ] ] [ PARTITION ( partition_name ) ];
VACUUM [ FULL [ COMPACT ] ] [ FREEZE ] [ VERBOSE ] [ table_name ] [ PARTITION ( partition_name ) ];
VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] { ANALYZE | ANALYSE } [ VERBOSE ]
    [ table_name [ (column_name [, ...] ) ] ] [ PARTITION ( partition_name ) ];
VACUUM DELTAMERGE [ table_name ];
VACUUM HDFSDIRECTORY [ table_name ];

VALUES

根据给定的值表达式计算一个或一组行的值。它通常用于在一个较大的命令内生成一个“常数表”。

VALUES {( expression [, ...] )} [, ...]
    [ ORDER BY {sort_expression [ ASC | DESC | USING operator ]} [, ...] ]
    [ LIMIT { count | ALL } ]
    [ OFFSET start [ ROW | ROWS ] ]
    [ FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY ];