How to generate the “create table” sql statement for an existing table in postgreSQL

Question

I have created a table in postgreSQL. I want to look at the SQL statement used to create the table but cannot figure it out.

How do I get the create table

Answer 1

Dean Toader Just excellent! I'd modify your code a little, to show all constraints in the table and to make possible to use regexp mask in table name.

CREATE OR REPLACE FUNCTION public.generate_create_table_statement(p_table_name character varying)
  RETURNS SETOF text AS
$BODY$
DECLARE
    v_table_ddl   text;
    column_record record;
    table_rec record;
    constraint_rec record;
    firstrec boolean;
BEGIN
    FOR table_rec IN
        SELECT c.relname FROM pg_catalog.pg_class c
            LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
                WHERE relkind = 'r'
                AND relname~ ('^('||p_table_name||')$')
                AND n.nspname <> 'pg_catalog'
                AND n.nspname <> 'information_schema'
                AND n.nspname !~ '^pg_toast'
                AND pg_catalog.pg_table_is_visible(c.oid)
          ORDER BY c.relname
    LOOP

        FOR column_record IN 
            SELECT 
                b.nspname as schema_name,
                b.relname as table_name,
                a.attname as column_name,
                pg_catalog.format_type(a.atttypid, a.atttypmod) as column_type,
                CASE WHEN 
                    (SELECT substring(pg_catalog.pg_get_expr(d.adbin, d.adrelid) for 128)
                     FROM pg_catalog.pg_attrdef d
                     WHERE d.adrelid = a.attrelid AND d.adnum = a.attnum AND a.atthasdef) IS NOT NULL THEN
                    'DEFAULT '|| (SELECT substring(pg_catalog.pg_get_expr(d.adbin, d.adrelid) for 128)
                                  FROM pg_catalog.pg_attrdef d
                                  WHERE d.adrelid = a.attrelid AND d.adnum = a.attnum AND a.atthasdef)
                ELSE
                    ''
                END as column_default_value,
                CASE WHEN a.attnotnull = true THEN 
                    'NOT NULL'
                ELSE
                    'NULL'
                END as column_not_null,
                a.attnum as attnum,
                e.max_attnum as max_attnum
            FROM 
                pg_catalog.pg_attribute a
                INNER JOIN 
                 (SELECT c.oid,
                    n.nspname,
                    c.relname
                  FROM pg_catalog.pg_class c
                       LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
                  WHERE c.relname = table_rec.relname
                    AND pg_catalog.pg_table_is_visible(c.oid)
                  ORDER BY 2, 3) b
                ON a.attrelid = b.oid
                INNER JOIN 
                 (SELECT 
                      a.attrelid,
                      max(a.attnum) as max_attnum
                  FROM pg_catalog.pg_attribute a
                  WHERE a.attnum > 0 
                    AND NOT a.attisdropped
                  GROUP BY a.attrelid) e
                ON a.attrelid=e.attrelid
            WHERE a.attnum > 0 
              AND NOT a.attisdropped
            ORDER BY a.attnum
        LOOP
            IF column_record.attnum = 1 THEN
                v_table_ddl:='CREATE TABLE '||column_record.schema_name||'.'||column_record.table_name||' (';
            ELSE
                v_table_ddl:=v_table_ddl||',';
            END IF;

            IF column_record.attnum <= column_record.max_attnum THEN
                v_table_ddl:=v_table_ddl||chr(10)||
                         '    '||column_record.column_name||' '||column_record.column_type||' '||column_record.column_default_value||' '||column_record.column_not_null;
            END IF;
        END LOOP;

        firstrec := TRUE;
        FOR constraint_rec IN
            SELECT conname, pg_get_constraintdef(c.oid) as constrainddef 
                FROM pg_constraint c 
                    WHERE conrelid=(
                        SELECT attrelid FROM pg_attribute
                        WHERE attrelid = (
                            SELECT oid FROM pg_class WHERE relname = table_rec.relname
                        ) AND attname='tableoid'
                    )
        LOOP
            v_table_ddl:=v_table_ddl||','||chr(10);
            v_table_ddl:=v_table_ddl||'CONSTRAINT '||constraint_rec.conname;
            v_table_ddl:=v_table_ddl||chr(10)||'    '||constraint_rec.constrainddef;
            firstrec := FALSE;
        END LOOP;
        v_table_ddl:=v_table_ddl||');';
        RETURN NEXT v_table_ddl;
    END LOOP;
END;
$BODY$
  LANGUAGE plpgsql VOLATILE
  COST 100;
ALTER FUNCTION public.generate_create_table_statement(character varying)
  OWNER TO postgres;

Now you can, for example, make the following query

SELECT * FROM generate_create_table_statement('.*');

which results like this:

CREATE TABLE public.answer (                                                                        
     id integer DEFAULT nextval('answer_id_seq'::regclass) NOT NULL,                               
     questionid integer  NOT NULL,                                                                  
     title character varying  NOT NULL,                                                             
     defaultvalue character varying  NULL,                                                          
     valuetype integer  NOT NULL,                                                                   
     isdefault boolean  NULL,                                                                       
     minval double precision  NULL,                                                                 
     maxval double precision  NULL,                                                                 
     followminmax integer DEFAULT 0 NOT NULL,                                                       
CONSTRAINT answer_pkey                                                                              
     PRIMARY KEY (id),                                                                              
CONSTRAINT answer_questionid_fkey                                                                  
     FOREIGN KEY (questionid) REFERENCES question(id) ON UPDATE RESTRICT ON DELETE RESTRICT,       
CONSTRAINT answer_valuetype_fkey                                                                   
     FOREIGN KEY (valuetype) REFERENCES answervaluetype(id) ON UPDATE RESTRICT ON DELETE RESTRICT);

for each user table.