postgreSQL 实现show create table

在mysql 中show create table 可以直接查询表的create sql 语句，在postgreSQL 没有这个命令，所以通过function 来实现，代码如下：

前提 定义一个公用的函数：findattname

CREATE OR REPLACE FUNCTION findattname(namespace character varying, tablename character varying, ctype character varying)
  RETURNS character varying AS
$BODY$

declare
tt oid ;
aname character varying default '';

begin
       tt := oid from pg_class where relname= tablename 
	and relnamespace =(select oid from pg_namespace  where nspname=namespace) ;
	-- select oid from pg_namespace where nspowner=(select datdba from pg_database where datname=namespace)
      
       aname:=  array_to_string(
		array(
		       select a.attname  from pg_attribute  a 
				where a.attrelid=tt and  a.attnum   in (		
				select unnest(conkey) from pg_constraint c where contype=ctype 
				and conrelid=tt  and array_to_string(conkey,',') is not null  
			) 
		),',')
	;
	
	return aname;
end 
	
	
    $BODY$
  LANGUAGE plpgsql VOLATILE
  COST 100;

showcreatetable：

CREATE OR REPLACE FUNCTION showcreatetable(namespace character varying, tablename character varying)
  RETURNS character varying AS
  
$BODY$
declare 
tableScript character varying default '';

begin
-- columns
tableScript:=tableScript || ' CREATE TABLE '|| tablename|| ' ( '|| array_to_string(
  array(
select concat( c1, c2, c3, c4, c5, c6 ) as column_line
from (
  select column_name || ' ' || data_type as c1,
    case when character_maximum_length > 0 then '(' || character_maximum_length || ')' end as c2,
    case when numeric_precision > 0 and numeric_scale < 1 then '(' || numeric_precision || ')' end as c3,
    case when numeric_precision > 0 and numeric_scale > 0 then '(' || numeric_precision || ', ' || numeric_scale || ')' end as c4,
    case when is_nullable = 'NO' then ' NOT NULL' end as c5,
    case when column_default is not Null then ' DEFAULT' end || ' ' || replace(column_default, '::character varying', '') as c6
  from information_schema.columns
  where table_name = tablename
  -- and table_schema=namespace
  order by ordinal_position
) as string_columns
),' , ') ||',' ;


-- 约束
tableScript:= tableScript || array_to_string(
array(
	select concat(' CONSTRAINT ',conname ,c ,u,p,f)   from (
		select conname,
		case when contype='c' then  ' CHECK('|| consrc ||')' end  as c  ,
		case when contype='u' then  ' UNIQUE('|| ( select findattname(namespace,tablename,'u') ) ||')' end as u ,
		case when contype='p' then ' PRIMARY KEY ('|| ( select findattname(namespace,tablename,'p') ) ||')' end  as p  ,
		case when contype='f' then ' FOREIGN KEY('|| ( select findattname(namespace,tablename,'u') ) ||') REFERENCES '|| 
		(select p.relname from pg_class p where p.oid=c.confrelid )  || '('|| ( select findattname(namespace,tablename,'u') ) ||')' end as  f
		from pg_constraint c
		where contype in('u','c','f','p') and conrelid=( 
			select oid  from pg_class  where relname=tablename and relnamespace =(
			select oid from pg_namespace where nspowner=(select datdba from pg_database where datname=namespace)
			)
		 )
	) as t  
) ,',' ) || ' ); ';
	
-- indexs 

-- CREATE UNIQUE INDEX pg_language_oid_index ON pg_language USING btree (oid); -- table pg_language


-- 
/** **/
--- 获取非约束索引 column
-- CREATE UNIQUE INDEX pg_language_oid_index ON pg_language USING btree (oid); -- table pg_language
tableScript:= tableScript || array_to_string(
	array(
		select 'CREATE UNIQUE INDEX ' || indexrelname || ' ON ' || tablename || ' USING btree '|| '(' || attname || ');' from (
		 SELECT 
		    i.relname AS indexrelname ,  x.indkey, 
		    ( select array_to_string (
			array( 
				select a.attname from pg_attribute a where attrelid=c.oid and a.attnum in ( select unnest(x.indkey) )

			     ) 
		     ,',' ) )as attname
		    
		   FROM pg_class c
		   JOIN pg_index x ON c.oid = x.indrelid
		   JOIN pg_class i ON i.oid = x.indexrelid
		   LEFT JOIN pg_namespace n ON n.oid = c.relnamespace
		   WHERE  c.relname=tablename and i.relname not in
			  ( select constraint_name from information_schema.key_column_usage  where  table_name=tablename  )
		)as t
) ,',' );
			

-- COMMENT COMMENT ON COLUMN sys_activity.id IS '主键';
tableScript:= tableScript || array_to_string(
array(
SELECT ' COMMENT ON COLUMN' || tablename || '.' || a.attname ||' IS  '|| ''''|| d.description ||''''
FROM pg_class c
JOIN pg_description d ON c.oid=d.objoid
JOIN pg_attribute a ON c.oid = a.attrelid
WHERE c.relname=tablename
AND a.attnum = d.objsubid),',') ;

return tableScript;

end
$BODY$
  LANGUAGE plpgsql VOLATILE
  COST 100;

 测试：

select showcreatetable('public','pg_seclabel');