进入psql命令行环境，可以使用的SQL命令如下：
pgdb=# \help可用帮助: ABORT CREATE LANGUAGE DROP VIEW ALTER AGGREGATE CREATE OPERATOR CLASS END ALTER CONVERSION CREATE OPERATOR EXECUTE ALTER DATABASE CREATE ROLE EXPLAIN ALTER DOMAIN CREATE RULE FETCH ALTER FUNCTION CREATE SCHEMA GRANT ALTER GROUP CREATE SEQUENCE INSERT ALTER INDEX CREATE TABLE LISTEN ALTER LANGUAGE CREATE TABLE AS LOAD ALTER OPERATOR CLASS CREATE TABLESPACE LOCK ALTER OPERATOR CREATE TRIGGER MOVE ALTER ROLE CREATE TYPE NOTIFY ALTER SCHEMA CREATE USER PREPARE ALTER SEQUENCE CREATE VIEW PREPARE TRANSACTION ALTER TABLE DEALLOCATE REINDEX ALTER TABLESPACE DECLARE RELEASE SAVEPOINT ALTER TRIGGER DELETE RESET ALTER TYPE DROP AGGREGATE REVOKE ALTER USER DROP CAST ROLLBACK ANALYZE DROP CONVERSION ROLLBACK PREPARED BEGIN DROP DATABASE ROLLBACK TO SAVEPOINT CHECKPOINT DROP DOMAIN SAVEPOINT CLOSE DROP FUNCTION SELECT CLUSTER DROP GROUP SELECT INTO COMMENT DROP INDEX SET COMMIT DROP LANGUAGE SET CONSTRAINTS COMMIT PREPARED DROP OPERATOR CLASS SET ROLE COPY DROP OPERATOR SET SESSION AUTHORIZATION CREATE AGGREGATE DROP ROLE SET TRANSACTION CREATE CAST DROP RULE SHOW CREATE CONSTRAINT TRIGGER DROP SCHEMA START TRANSACTION CREATE CONVERSION DROP SEQUENCE TRUNCATE CREATE DATABASE DROP TABLE UNLISTEN CREATE DOMAIN DROP TABLESPACE UPDATE CREATE FUNCTION DROP TRIGGER VACUUM CREATE GROUP DROP TYPE CREATE INDEX DROP USER比如，要获得SQL命令create database的帮助，则输出如下信息：
pgdb=# \help create database命令: CREATE DATABASE描述: 创建一个新的数据库语法:CREATE DATABASE name [ [ WITH ] [ OWNER [=] dbowner ] [ TEMPLATE [=] template ] [ ENCODING [=] encoding ] [ TABLESPACE [=] tablespace ] [ CONNECTION LIMIT [=] connlimit ] ]pgdb=#
