注意：实在一项技能最好的辅助课本就是它的官方文档；（PostgreSQL 12.2 手册） PG的官方文档环视不错的，相比较Oracle和MongoDB的官方文档，技能比较全且是比较正确的中文翻译；
注意：psql 的命令都是以斜杠 "\" 开头的。
(1) \l 查看全部数据库
（2）\d [ pattern ] 该命令将表现每个匹配关系（表、视图、索引、序列）的信息，可以加上 + 查看更多的信息，如 \d+
不加任何参数表示查看当前数据库的全部表。
\d tablename 背面跟一个表名，表示表现这个表的布局定义
\d indexname 也可以表现索引的信息，如 \d 索引名称
\d * 背面也可以跟通配符如 "*" 或 "?"，\d x*
\d+ 将表现比 \d 更具体的信息，还会表现任何与表关系的注释，以及表中出现的 OID
\dt 只表现匹配的表
\di 只表现索引
\ds 只表现序列
\dv 只表现视图
\df 只表现函数
(3) \timing on或off 表现 SQL 已执行的时间，默认环境下是 off
(4)\dn 列出全部的 schema
(5)\du 或 \dg 列出全部的数据库用户和角色
(6)\db 表现全部的表空间，表空间实在是一个目录，放在这个表空间的表，就是把表的数据文件发到这个表空间下。
(7)\dp 或 \z 表现表的权限分配环境
(8)\encoding 指定客户端的字符编码，如 \encoding UTF8;
(9)\pset 设置输出的格式，\pset border 0 : 表示输出内容无边框。 border 1 ：表示边框只在内部。border 2 ：内外都有边框
(10)\x 把表中的每一行的每列数据都拆分为单行展示，与 MySQL 中的 "\G" 的功能雷同。
(11)\echo 用于输出一行信息，通常用于在 .sql 文件中输出一些提示信息。
(12)\password 设置密码
(13)\conninfo 列出当前数据库连接的信息
(14)\dx 查看数据库中安装的扩展 或 select * from pg_extension; 全部的\用法：
General
\copyright show PostgreSQL usage and distribution terms
\crosstabview [COLUMNS] execute query and display results in crosstab
\errverbose show most recent error message at maximum verbosity
\g [FILE] or ; execute query (and send results to file or |pipe)
\gdesc describe result of query, without executing it
\gexec execute query, then execute each value in its result
\gset [PREFIX] execute query and store results in psql variables
\gx [FILE] as \g, but forces expanded output mode
\q quit psql
\watch [SEC] execute query every SEC seconds
Help
\? [commands] show help on backslash commands
\? options show help on psql command-line options
\? variables show help on special variables
\h [NAME] help on syntax of SQL commands, * for all commands
Query Buffer
\e [FILE] [LINE] edit the query buffer (or file) with external editor
\ef [FUNCNAME [LINE]] edit function definition with external editor
\ev [VIEWNAME [LINE]] edit view definition with external editor
\p show the contents of the query buffer
\r reset (clear) the query buffer
\s [FILE] display history or save it to file
\w FILE write query buffer to file
Input/Output
\copy ... perform SQL COPY with data stream to the client host
\echo [STRING] write string to standard output
\i FILE execute commands from file
\ir FILE as \i, but relative to location of current script
\o [FILE] send all query results to file or |pipe
\qecho [STRING] write string to query output stream (see \o)
Conditional
\if EXPR begin conditional block
\elif EXPR alternative within current conditional block
\else final alternative within current conditional block
\endif end conditional block
Informational
(options: S = show system objects, + = additional detail)
\d[S+] list tables, views, and sequences
\d[S+] NAME describe table, view, sequence, or index
\da[S] [PATTERN] list aggregates
\dA[+] [PATTERN] list access methods
\db[+] [PATTERN] list tablespaces
\dc[S+] [PATTERN] list conversions
\dC[+] [PATTERN] list casts
\dd[S] [PATTERN] show object descriptions not displayed elsewhere
\dD[S+] [PATTERN] list domains
\ddp [PATTERN] list default privileges
\dE[S+] [PATTERN] list foreign tables
\det[+] [PATTERN] list foreign tables
\des[+] [PATTERN] list foreign servers
\deu[+] [PATTERN] list user mappings
\dew[+] [PATTERN] list foreign-data wrappers
\df[anptw][S+] [PATRN] list [only agg/normal/procedures/trigger/window] functio
ns
\dF[+] [PATTERN] list text search configurations
\dFd[+] [PATTERN] list text search dictionaries
\dFp[+] [PATTERN] list text search parsers
\dFt[+] [PATTERN] list text search templates
\dg[S+] [PATTERN] list roles
\di[S+] [PATTERN] list indexes
\dl list large objects, same as \lo_list
\dL[S+] [PATTERN] list procedural languages
\dm[S+] [PATTERN] list materialized views
\dn[S+] [PATTERN] list schemas
\do[S] [PATTERN] list operators
\dO[S+] [PATTERN] list collations
\dp [PATTERN] list table, view, and sequence access privileges
\dP[itn+] [PATTERN] list [only index/table] partitioned relations [n=nested]
\drds [PATRN1 [PATRN2]] list per-database role settings
\dRp[+] [PATTERN] list replication publications
\dRs[+] [PATTERN] list replication subscriptions
\ds[S+] [PATTERN] list sequences
\dt[S+] [PATTERN] list tables
\dT[S+] [PATTERN] list data types
\du[S+] [PATTERN] list roles
\dv[S+] [PATTERN] list views
\dx[+] [PATTERN] list extensions
\dy [PATTERN] list event triggers
\l[+] [PATTERN] list databases
\sf[+] FUNCNAME show a function's definition
\sv[+] VIEWNAME show a view's definition
\z [PATTERN] same as \dp
Formatting
\a toggle between unaligned and aligned output mode
\C [STRING] set table title, or unset if none
\f [STRING] show or set field separator for unaligned query output
\H toggle HTML output mode (currently off)
\pset [NAME [VALUE]] set table output option
(border|columns|csv_fieldsep|expanded|fieldsep|
fieldsep_zero|footer|format|linestyle|null|
numericlocale|pager|pager_min_lines|recordsep|
recordsep_zero|tableattr|title|tuples_only|
unicode_border_linestyle|unicode_column_linestyle|
unicode_header_linestyle)
\t [on|off] show only rows (currently off)
\T [STRING] set HTML <table> tag attributes, or unset if none
\x [on|off|auto] toggle expanded output (currently off)
Connection
\c[onnect] {[DBNAME|- USER|- HOST|- PORT|-] | conninfo}
connect to new database (currently "postgres")
\conninfo display information about current connection
\encoding [ENCODING] show or set client encoding
\password [USERNAME] securely change the password for a user
Operating System
\cd [DIR] change the current working directory
\setenv NAME [VALUE] set or unset environment variable
\timing [on|off] toggle timing of commands (currently off)
\! [COMMAND] execute command in shell or start interactive shell
Variables
\prompt [TEXT] NAME prompt user to set internal variable
\set [NAME [VALUE]] set internal variable, or list all if no parameters
\unset NAME unset (delete) internal variable
Large Objects
\lo_export LOBOID FILE
\lo_import FILE [COMMENT]
\lo_list
\lo_unlink LOBOID large object operations
4.2执行存储在外部文件中的 SQL 命令
