Pl/PgSQL, insert into two tables, one with header rows - sql

Question

What would be the best way of going about doing the following insert. I've looked around, and I'm kind of stuck.
The table I Currently have (insert)
| id | order_id | item_id | type | group |
| 1 | 1 | 1 | 2 | 1 | <- type 2 represents a "header" item, or a "kit"
| 2 | 1 | 2 | 1 | 1 | <- type 1 represents a member of the "kit"
| 3 | 1 | 3 | 1 | 1 |
| 4 | 1 | 4 | 2 | 2 | <- New group means new kit
| 5 | 1 | 2 | 1 | 2 |
| 6 | 1 | 5 | 1 | 2 |
I need to insert these items into the following two tables:
1) item_entry
| id | mode | tmplt_id | item_id | parent_item_entry_id |
| 1 | 1 | 1 | NULL | NULL | <- This is a header line, mode 1
| 2 | 2 | NULL | 2 | 1 | <- This is a sub line, mode 2
| 3 | 2 | NULL | 3 | 1 | <- parent_item_entry_id references the header it belongs to
| 4 | 1 | 4 | NULL | NULL |
| 5 | 2 | NULL | 2 | 4 |
| 6 | 2 | NULL | 5 | 4 |
2) item_entry_details
| id | item_entry_id | order_id | group |
| 1 | 1 | 1 | 1 |
| 2 | 4 | 1 | 2 | <- only header information is necessary
Of course, item_entry.id is driven off of a sequence (item_entry_id_seq). Is there an elegent way of getting this to work? I currently loop through each group, first assigning a nextval() to a variable, and then I loop through each item in the group, writing to the table.
FOR recGroup IN SELECT DISTINCT group FROM insert LOOP
intParentItemEntryID := nextval('item_entry_id_seq');
FOR recLine IN SELECT * FROM insert LOOP
INSERT INTO item_entry VALUES (CASE intParentItemEntryID/DEFAULT, CASE 1/2, CASE recLine.item_id/NULL, CASE NULL/recLine.item_id, CASE NULL/intParentItemEntryID)
INSERT INTO item_entry_details VALUES (DEFAULT, intParentItemEntryID, recLine.order_id, recLine.group);
END LOOP;
END LOOP;
Is there a better way, or is the above the only way this type of insert can be done?

Answer 1

No need for procedural code "row-at-a-time" here, just plain old sql will suffice.
-- create the tables that the OP did not provide
DROP TABLE the_input;
CREATE TABLE the_input
( id INTEGER NOT NULL PRIMARY KEY
, order_id INTEGER NOT NULL
, item_id INTEGER NOT NULL
, ztype INTEGER NOT NULL
, zgroup INTEGER NOT NULL
);
DROP TABLE target1 ;
CREATE TABLE target1
( id INTEGER NOT NULL
, zmode INTEGER NOT NULL
, tmplt_id INTEGER
, item_id INTEGER
, parent_item_entry_id INTEGER
);
DROP TABLE target2 ;
CREATE TABLE target2
( id SERIAL NOT NULL
, item_entry_id INTEGER NOT NULL
, order_id INTEGER NOT NULL
, zgroup INTEGER NOT NULL
);
-- fil it up ...
INSERT INTO the_input
( id, order_id, item_id, ztype, zgroup ) VALUES
( 1 , 1 , 1 , 2 , 1 ) -- <- type 2 represents a "header" item, or a "kit"
,( 2 , 1 , 2 , 1 , 1 ) -- <- type 1 represents a member of the "kit"
,( 3 , 1 , 3 , 1 , 1 ) --
,( 4 , 1 , 4 , 2 , 2 ) -- <- New group means new kit
,( 5 , 1 , 2 , 1 , 2 ) --
,( 6 , 1 , 5 , 1 , 2 ) --
;
-- Do the inserts.
INSERT INTO target1(id,zmode,tmplt_id,item_id,parent_item_entry_id)
SELECT i1.id, 1, i1.id, NULL, NULL
FROM the_input i1
WHERE i1.ztype=2
UNION ALL
SELECT i2.id, 2, NULL, i2.id, ip.item_id
FROM the_input i2
JOIN the_input ip ON ip.zgroup = i2.zgroup AND ip.ztype=2
WHERE i2.ztype=1
;
INSERT INTO target2(item_entry_id,order_id,zgroup)
SELECT DISTINCT MIN(item_id),order_id, zgroup
FROM the_input i1
WHERE i1.ztype=2
GROUP BY order_id,zgroup
;
SELECT * FROM target1
ORDER BY id;
SELECT * FROM target2
ORDER BY id;
Result:
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "the_input_pkey" for table "the_input"
CREATE TABLE
INSERT 0 6
DROP TABLE
CREATE TABLE
INSERT 0 6
id | zmode | tmplt_id | item_id | parent_item_entry_id
----+-------+----------+---------+----------------------
1 | 1 | 1 | |
2 | 2 | | 2 | 1
3 | 2 | | 3 | 1
4 | 1 | 4 | |
5 | 2 | | 5 | 4
6 | 2 | | 6 | 4
(6 rows)
DROP TABLE
NOTICE: CREATE TABLE will create implicit sequence "target2_id_seq" for serial column "target2.id"
CREATE TABLE
INSERT 0 2
id | item_entry_id | order_id | zgroup
----+---------------+----------+--------
1 | 4 | 1 | 2
2 | 1 | 1 | 1
(2 rows)