Query SQL Select Column Matching From Another Table - sql

Question

edit : Sorry gurus, I have to rephrase my question since I forgot there are 3 tables in one query.
I have three tables with tbl_goods ,tbl_units and tbl_sat which looks like this :
tbl_goods, consists of sold goods
+--------+-------+-------+-------+
| goods |code |qty |unit |
+--------+-------+-------+-------+
| cigar | G001 | 1 | pack |
| cigar | G001 | 2 | pcs |
| bread | G002 | 2 | pcs |
| soap | G003 | 1 | pcs |
+--------+-------+-------+-------+
and tbl_units as below :
+--------+-------------+-------+
| code |ucode |qty |
+--------+-------------+-------+
| KG001 | U001 | 10 |
+--------+-------------+-------+
I add letter 'K' in front of code in tbl_units to differ and make sure not collide with code in tbl_goods.
and tbl_sat as below :
+--------+-------------+
| ucode | unit |
+--------+-------------+
| U001 | pack |
+--------+-------------+
| U002 | box |
+--------+-------------+
| U003 | crate | etc
so only cigar will have conversion because table units have the code
what the result I need to show as below :
+--------+-------+-------+-------+--------+
| goods |code |qty |unit | total |
+--------+-------+-------+-------+--------+
| cigar | G001 | 1 | pack | 10 |
| cigar | G001 | 2 | pcs | 2 |
| bread | G002 | 2 | pcs | 2 |
| soap | G003 | 1 | pcs | 1 |
+--------+-------+-------+-------+--------+
so if the code in goods doesn't have match in tbl_units then it will show just as qty in tbl_goods, but if they match then it will convert multiply from tbl_units
Thank you very much..really appreciated
regards
EDIT (might worked ?) :
I try to modify from #danielpr query, and this is the result
think it worked, please help to check it out
SELECT j.code,j.qty ,j.unit, IIF(j.unit=t.unit,j.qty*u.qty,j.fqty) FROM tbl_goods j
LEFT JOIN tbl_units u on u.code ='K' || j.code
LEFT JOIN tbl_sat t ON t.ucode =u.ucode [WHERE j.code='G001']
GROUP BY j.code,j.qty
[WHERE ..] optional if omitted will list all items, but if I just want to check the cigar..just put WHERE CLAUSE

Answer 1

If I understand correct, you are looking for a combination of LEFT JOIN and CASE WHEN or COALESCE.
Here the CASE WHEN option:
SELECT g.goods, g.code, g.qty, g.unit,
CASE WHEN u.conversion IS NULL
THEN g.qty
ELSE g.qty * u.qty
END AS total
FROM
tbl_goods g
LEFT JOIN tbl_units u
ON g.code = u.code
AND g.unit = u.conversion;
As said, COALESCE could also do and is a bit shorter:
SELECT g.goods, g.code, g.qty, g.unit,
g.qty * COALESCE(u.qty,1) AS total
FROM
tbl_goods g
LEFT JOIN tbl_units u
ON g.code = u.code
AND g.unit = u.conversion;
But I think this option has a worse readability compared to CASE WHEN.
Therefore, I would prefer CASE WHEN here.
Try out: db<>fiddle
EDIT because the authour changed the question:
According to the new description, a further table is involved and the table structure is other than described before. So, the COALESCE option is not possible at all in this case.
We require the CASE WHEN way here:
SELECT g.goods, g.code, g.qty, g.unit,
CASE WHEN u.qty IS NULL OR u.ucode IS NULL OR t.unit IS NULL
THEN g.qty
ELSE g.qty * u.qty
END AS total
FROM
tbl_goods g
LEFT JOIN tbl_units u ON u.code = CONCAT('K', g.code)
LEFT JOIN tbl_sat t ON u.ucode = t.ucode AND g.unit = t.unit;
New sample fiddle for this new situation: db<>fiddle

Answer 2

SELECT
tbl_goods.goods
, tbl_goods.code
, tbl_goods.qty
, tbl_goods.unit
, IF(tbl_goods.unit=tbl_units.conversion,tbl_goods.qty*tbl_units.qty,tbl_goods.qty) total
FROM tbl_goods
LEFT JOIN tbl_units ON tbl_goods.code=tbl_units.code
on total column, we can match whether the unit in tbl_goods is same with tbl_units, which is pack.
If it is the same, then we multiply the pack qty in tbl_units with the pack in tbl_goods, else, just return the qty of tbl_goods.