[PostgreSQL] psql

1. \pset 命令
1-1. NULL 的显示
=# \pset null (NULL)
Null display is "(NULL)".


2. 显示发送到服务端的所有命令
2-1. 启动 psql 时设置
psql -E
2-2. 在 psql 中设置
=# \set ECHO_HIDDEN on
=# \set ECHO_HIDDEN off
=# \echo :ECHO_HIDDEN

ECHO_HIDDEN 设置 off 之后
=# \df array_to_json
********* QUERY **********
SELECT n.nspname as "Schema",
  p.proname as "Name",
  pg_catalog.pg_get_function_result(p.oid) as "Result data type",
  pg_catalog.pg_get_function_arguments(p.oid) as "Argument data types",
 CASE
  WHEN p.proisagg THEN 'agg'
  WHEN p.proiswindow THEN 'window'
  WHEN p.prorettype = 'pg_catalog.trigger'::pg_catalog.regtype THEN 'trigger'
  ELSE 'normal'
END as "Type"
FROM pg_catalog.pg_proc p
     LEFT JOIN pg_catalog.pg_namespace n ON n.oid = p.pronamespace
WHERE p.proname ~ '^(array_to_json)$'
  AND pg_catalog.pg_function_is_visible(p.oid)
ORDER BY 1, 2, 4;
**************************

                              List of functions
   Schema   |     Name      | Result data type | Argument data types |  Type 
------------+---------------+------------------+---------------------+--------
 pg_catalog | array_to_json | json             | anyarray            | normal
 pg_catalog | array_to_json | json             | anyarray, boolean   | normal
(2 rows)


3. 连接数据库
=# \c dbname username host port
=# \connect dbname username host port