PostgreSQL查看表结构语句

参考​​https://www.modb.pro/db/60164​​

在PG里面查看表结构，不如mysql那样show create table xx 这样方便。 

在PG里面常用如下3种方法：

第一种，最朴实的方法就是 pg_dump  --schema-only   导出全部的表结构

第二种，创建一个function，具体如下：

CREATE OR REPLACE FUNCTION tabledef(text,text) RETURNS text
LANGUAGE sql STRICT AS 
$$
WITH attrdef AS (
        SELECT n.nspname, c.relname, c.oid, pg_catalog.array_to_string(c.reloptions || array(select 'toast.' || x from pg_catalog.unnest(tc.reloptions) x), ', ') as relopts,
        c.relpersistence, a.attnum, a.attname, pg_catalog.format_type(a.atttypid, a.atttypmod) as atttype, 
        (SELECT substring(pg_catalog.pg_get_expr(d.adbin, d.adrelid, true) for 128) FROM pg_catalog.pg_attrdef d WHERE d.adrelid = a.attrelid AND d.adnum = a.attnum AND a.atthasdef) as attdefault,
        a.attnotnull, (SELECT c.collname FROM pg_catalog.pg_collation c, pg_catalog.pg_type t WHERE c.oid = a.attcollation AND t.oid = a.atttypid AND a.attcollation <> t.typcollation) as attcollation,
        a.attidentity, a.attgenerated 
        FROM pg_catalog.pg_attribute a 
        JOIN pg_catalog.pg_class c ON a.attrelid = c.oid 
        JOIN pg_catalog.pg_namespace n ON c.relnamespace = n.oid 
        LEFT JOIN pg_catalog.pg_class tc ON (c.reltoastrelid = tc.oid) 
        WHERE n.nspname = $1 AND c.relname = $2 AND a.attnum > 0 AND NOT a.attisdropped 
        ORDER BY a.attnum
    ), coldef AS (
        SELECT attrdef.nspname, attrdef.relname, attrdef.oid, attrdef.relopts, attrdef.relpersistence, pg_catalog.format('%I %s%s%s%s%s', attrdef.attname, attrdef.atttype, 
        case when attrdef.attcollation is null then '' else pg_catalog.format(' COLLATE %I', attrdef.attcollation) end, 
        case when attrdef.attnotnull then ' NOT NULL' else '' end, 
        case when attrdef.attdefault is null then '' else case when attrdef.attgenerated = 's' then pg_catalog.format(' GENERATED ALWAYS AS (%s) STORED', attrdef.attdefault) when attrdef.attgenerated <> '' then ' GENERATED AS NOT_IMPLEMENTED' else pg_catalog.format(' DEFAULT %s', attrdef.attdefault)  end  end,           
        case when attrdef.attidentity<>'' then pg_catalog.format(' GENERATED %s AS IDENTITY', case attrdef.attidentity when 'd' then 'BY DEFAULT' when 'a' then 'ALWAYS' else 'NOT_IMPLEMENTED' end)       else '' end ) as col_create_sql    
        FROM attrdef
        ORDER BY attrdef.attnum
    ), tabdef AS (
         SELECT coldef.nspname, coldef.relname, coldef.oid, coldef.relopts, coldef.relpersistence, concat(string_agg(coldef.col_create_sql, E',\n    ') , (select concat(E',\n    ',pg_get_constraintdef(oid)) from pg_constraint where contype='p' and conrelid = coldef.oid))  as cols_create_sql
         FROM coldef 
         GROUP BY coldef.nspname, coldef.relname, coldef.oid, coldef.relopts, coldef.relpersistence
    )
SELECT FORMAT( 'CREATE%s TABLE %I.%I%s%s%s;', 
                case tabdef.relpersistence when 't' then ' TEMP' when 'u' then ' UNLOGGED' else '' end, 
                tabdef.nspname, 
                tabdef.relname, 
                coalesce( (
                        SELECT FORMAT( E'\n    PARTITION OF %I.%I %s\n', pn.nspname, pc.relname, pg_get_expr(c.relpartbound, c.oid) ) 
                        FROM pg_class c 
                        JOIN pg_inherits i ON c.oid = i.inhrelid
                        JOIN pg_class pc ON pc.oid = i.inhparent
                        JOIN pg_namespace pn ON pn.oid = pc.relnamespace
                        WHERE c.oid = tabdef.oid ),
                        FORMAT( E' (\n    %s\n)', tabdef.cols_create_sql) 
                ),
                case when tabdef.relopts <> '' then format(' WITH (%s)', tabdef.relopts) else '' end,
                coalesce(E'\nPARTITION BY '||pg_get_partkeydef(tabdef.oid), '') 
            ) as table_create_sql
FROM tabdef
$$;


效果：
=# select tabledef('public','pgbench_accounts');
                tabledef                
────────────────────────────────────────
 CREATE TABLE public.pgbench_accounts (↵
     aid integer NOT NULL,             ↵
     bid integer,                      ↵
     abalance integer,                 ↵
     filler character(84),             ↵
     PRIMARY KEY (aid)                 ↵
 ) WITH (fillfactor=100);
(1
row)

注意：

1、这个function是database级别的，如果换到其它database 需要重建创建function。

2、经测试，支持view的导出查看

3、经测试，得出的建表语句中，是不会带有外键的信息，如果用到了外键的请注意！

第三种，使用pgddl插件​

要使用root用户安装此插件，并在安装时设置好环境变量。 稍微费点事。感兴趣的可以看官方文档​​https://github.com/lacanoid/pgddl​​