postgresql中的临时表

前言

参考：

Postgresql中临时表（temporary table）的特性和用法

【PostgreSQL-9.6.3】临时表

PostgreSQL SELECT INTO和INSERT INTO SELECT 两种表复制语句

如何在postgresql 函数中创建临时表？？？

结论

临时表解释：

PostgreSQL中的临时表分两种，一种是会话级临时表，一种是事务级临时表。在会话级临时表中，数据可以存在于整个会话的生命周期中，在事务级临时表中的数据只能存在于事务的生命周期中。

1. 不管是会话级还是事务级的临时表，当会话结束后，临时表会消失，这和Oracle数据库不同。Oracle数据库当会话结束后，数据消失，而表依然存在。
2. “ON COMMIT” 子句有三种形式,默认使用的是PRESERVE ROWS：
   (1)ON COMMIT PRESERVE ROWS 表示临时表的数据在事务结束后保留;
   (2)ON COMMIT DELETE ROWS 表示临时表的数据在事务结束后truncate掉;
   (3)ON COMMIT DROP 表示临时表在事务结束后删除。

临时表命令：

CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXISTS ] table_name ( [
  { column_name data_type [ COLLATE collation ] [ column_constraint [ ... ] ]
    | table_constraint
    | LIKE source_table [ like_option ... ] }
    [, ... ]
] )
[ INHERITS ( parent_table [, ... ] ) ]
[ PARTITION BY { RANGE | LIST } ( { column_name | ( expression ) } [ COLLATE collation ] [ opclass ] [, ... ] ) ]
[ WITH ( storage_parameter [= value] [, ... ] ) | WITH OIDS | WITHOUT OIDS ]
[ ON COMMIT { PRESERVE ROWS | DELETE ROWS | DROP } ]
[ TABLESPACE tablespace_name ]

CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXISTS ] table_name
    OF type_name [ (
  { column_name [ WITH OPTIONS ] [ column_constraint [ ... ] ]
    | table_constraint }
    [, ... ]
) ]
[ PARTITION BY { RANGE | LIST } ( { column_name | ( expression ) } [ COLLATE collation ] [ opclass ] [, ... ] ) ]
[ WITH ( storage_parameter [= value] [, ... ] ) | WITH OIDS | WITHOUT OIDS ]
[ ON COMMIT { PRESERVE ROWS | DELETE ROWS | DROP } ]
[ TABLESPACE tablespace_name ]

CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXISTS ] table_name
    PARTITION OF parent_table [ (
  { column_name [ WITH OPTIONS ] [ column_constraint [ ... ] ]
    | table_constraint }
    [, ... ]
) ] FOR VALUES partition_bound_spec
[ PARTITION BY { RANGE | LIST } ( { column_name | ( expression ) } [ COLLATE collation ] [ opclass ] [, ... ] ) ]
[ WITH ( storage_parameter [= value] [, ... ] ) | WITH OIDS | WITHOUT OIDS ]
[ ON COMMIT { PRESERVE ROWS | DELETE ROWS | DROP } ]
[ TABLESPACE tablespace_name ]

where column_constraint is:

[ CONSTRAINT constraint_name ]
{ NOT NULL |
  NULL |
  CHECK ( expression ) [ NO INHERIT ] |
  DEFAULT default_expr |
  GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY [ ( sequence_options ) ] |
  UNIQUE index_parameters |
  PRIMARY KEY index_parameters |
  REFERENCES reftable [ ( refcolumn ) ] [ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ]
    [ ON DELETE action ] [ ON UPDATE action ] }
[ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]

and table_constraint is:

[ CONSTRAINT constraint_name ]
{ CHECK ( expression ) [ NO INHERIT ] |
  UNIQUE ( column_name [, ... ] ) index_parameters |
  PRIMARY KEY ( column_name [, ... ] ) index_parameters |
  EXCLUDE [ USING index_method ] ( exclude_element WITH operator [, ... ] ) index_parameters [ WHERE ( predicate ) ] |
  FOREIGN KEY ( column_name [, ... ] ) REFERENCES reftable [ ( refcolumn [, ... ] ) ]
    [ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ] [ ON DELETE action ] [ ON UPDATE action ] }
[ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]

and like_option is:

{ INCLUDING | EXCLUDING } { COMMENTS | CONSTRAINTS | DEFAULTS | IDENTITY | INDEXES | STATISTICS | STORAGE | ALL }

and partition_bound_spec is:

IN ( { numeric_literal | string_literal | TRUE | FALSE | NULL } [, ...] ) |
FROM ( { numeric_literal | string_literal | TRUE | FALSE | MINVALUE | MAXVALUE } [, ...] )
  TO ( { numeric_literal | string_literal | TRUE | FALSE | MINVALUE | MAXVALUE } [, ...] )

index_parameters in UNIQUE, PRIMARY KEY, and EXCLUDE constraints are:

[ WITH ( storage_parameter [= value] [, ... ] ) ]
[ USING INDEX TABLESPACE tablespace_name ]

exclude_element in an EXCLUDE constraint is:

{ column_name | ( expression ) } [ opclass ] [ ASC | DESC ] [ NULLS { FIRST | LAST } ]

来自 postgresql10手册。

临时表的两种初始化方式。

1、第一种，正正经经创建临时表，然后批量导入数据。

就是这种方式，请原谅我盗图了。。
这种方式用处不是很方便。使用上有限制。个人感觉临时表最好不用每个字段都定义，毕竟有些数据集需要先存储起来再处理，你总不能这样定义吧。

2、第二种直接从结果集创建。

create [temporary] table as select * from 目标表。

请原谅我引用信息：

好了，大体的创建方式是：

create temporary table "tmp_tbl_001" on commit drop as select * from member;

select * from tmp_tbl_001;

看看结果：

这种引用方式很好，可以直接保存又不用事先定义。