PostgreSQL学习第八篇--psql的使用技巧和注意事项

1.历史命令与补全功能
可以使用上下键把以前使用过的命令或SQL语句调出来。
连续按两个tab键表示命令补全或者提示输入。--类似于Linux功能

2.自动提交方面的技巧
在psql中，事务是自动提交的。（与oracle不同）
如果不想自动提交，可以：
    默认，postgresql是自动提交的，可以避免自动提交 
    1）使用begin;命令 
      示例： 
    postgres=# begin; 
    BEGIN 
    postgres=# insert into test values(2,2); 
    INSERT 0 1 
    postgres=# select * from test; 
     id | name 
    ----+------ 
      1 | 
      1 |    2 
      2 |    2 
    (3 行记录) 


    postgres=# rollback; 
    ROLLBACK 
    postgres=# select * from test; 
     id | name 
    ----+------ 
      1 | 
      1 |    2 
    (2 行记录) 

    2）还可以直接关闭自动提交的功能 
    \set AUTOCOMMIT off  --注意，AUTOCOMMIT要大写。
    示例： 
    postgres=# \set AUTOCOMMIT off 
    postgres=# 
    postgres=# 
    postgres=# insert into test values(2,2); 
    INSERT 0 1 
    postgres=# select * from test; 
     id | name 
    ----+------ 
      1 | 
      1 |    2 
      2 |    2 
    (3 行记录) 


    postgres=# rollback; 
    ROLLBACK 
    postgres=# select * from test; 
     id | name 
    ----+------ 
      1 | 
      1 |    2 
    (2 行记录)

3.得到psql命令行中具体执行的SQL语句
启动psql时加上-E参数，或者在命令行中使用\set ECHO_HIDDEN on|off命令。
[postgres@single ~]$ psql -E
psql (9.6.1)
Type "help" for help.

postgres=# \d
********* QUERY **********
SELECT n.nspname as "Schema",
  c.relname as "Name",
  CASE c.relkind WHEN 'r' THEN 'table' WHEN 'v' THEN 'view' WHEN 'm' THEN 'materialized view' WHEN 'i' THEN 'index' WHEN 'S' THEN 'sequence' WHEN 's' THEN 'special' WHEN 'f' THEN 'foreign table' END as "Type",
  pg_catalog.pg_get_userbyid(c.relowner) as "Owner"
FROM pg_catalog.pg_class c
     LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
WHERE c.relkind IN ('r','v','m','S','f','')
      AND n.nspname <> 'pg_catalog'
      AND n.nspname <> 'information_schema'
      AND n.nspname !~ '^pg_toast'
  AND pg_catalog.pg_table_is_visible(c.oid)
ORDER BY 1,2;
**************************

        List of relations
 Schema | Name | Type  |  Owner   
--------+------+-------+----------
 public | test | table | postgres
 public | txx  | table | postgres
(2 rows)

postgres=# \set ECHO_HIDDEN off
postgres=# \d
        List of relations
 Schema | Name | Type  |  Owner   
--------+------+-------+----------
 public | test | table | postgres
 public | txx  | table | postgres
(2 rows)

postgres=# \set ECHO_HIDDEN on
postgres=# \d
********* QUERY **********
SELECT n.nspname as "Schema",
  c.relname as "Name",
  CASE c.relkind WHEN 'r' THEN 'table' WHEN 'v' THEN 'view' WHEN 'm' THEN 'materialized view' WHEN 'i' THEN 'index' WHEN 'S' THEN 'sequence' WHEN 's' THEN 'special' WHEN 'f' THEN 'foreign table' END as "Type",
  pg_catalog.pg_get_userbyid(c.relowner) as "Owner"
FROM pg_catalog.pg_class c
     LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
WHERE c.relkind IN ('r','v','m','S','f','')
      AND n.nspname <> 'pg_catalog'
      AND n.nspname <> 'information_schema'
      AND n.nspname !~ '^pg_toast'
  AND pg_catalog.pg_table_is_visible(c.oid)
ORDER BY 1,2;
**************************

        List of relations
 Schema | Name | Type  |  Owner   
--------+------+-------+----------
 public | test | table | postgres
 public | txx  | table | postgres
(2 rows)