Mysql5.6 select statement with duplicate id and set - mysql

Question

I have a table A containing id (auto incremented) as a primary key and a table B containing id as a foreign key.While selecting data from Table B if there are duplicate ids then append a number with empid.
TableA
id empid name place
1 ab123 John SL
2 gh345 Lucy AK
3 hj890 Mike KL
TableB
id class
1 A
1 B
1 A
2 A
3 A
Output
ab123,SL,A
ab123,SL,B
ab123,SL,A
gh345,AK,A
hj890,KL,A
Desired output
ab123-1,SL,A
ab123-2,SL,B
ab123-3,SL,A
gh345,AK,A
hj890,KL,A
This is what I have tried
SELECT TableA.empid, ",", TableA.place, ",", TableB.class
FROM TableA
INNER JOIN TableB ON TableA.id = TableB.id

Answer 1

With mysql 8 You can do following code, in mysql 6.x you need to use user-defined variables instead of the window finction
CREATE TABLE TableA (
`id` INTEGER,
`empid` VARCHAR(5),
`name` VARCHAR(4),
`place` VARCHAR(2)
);
INSERT INTO TableA
(`id`, `empid`, `name`, `place`)
VALUES
('1', 'ab123', 'John', 'SL'),
('2', 'gh345', 'Lucy', 'AK'),
('3', 'hj890', 'Mike', 'K');
CREATE TABLE TableB (
`id` INTEGER,
`class` VARCHAR(1)
);
INSERT INTO TableB
(`id`, `class`)
VALUES
('1', 'A'),
('1', 'B'),
('1', 'A'),
('2', 'A'),
('3', 'A');
SELECT CONCAT(`empid`,IF(co > 1,CONCAT('-',`rn`),''),',',`place`,',',`class`) AS 'empid,place,class'
FROM
(SELECT
empid,place,class, ROW_NUMBER() OVER (PARTITION BY empid ) rn
, countB.co
FROM TableA
INNER JOIN TableB ON TableA.id = TableB.id
INNER JOIN (SELECT id,COUNT(*) co FROM TableB GROUP BY id) countB ON TableB.id = countB.id) t1
| empid,place,class |
| :---------------- |
| ab123-1,SL,A |
| ab123-2,SL,B |
| ab123-3,SL,A |
| gh345,AK,A |
| hj890,K,A |
db<>fiddle here
MySQL 5.x Version
SELECT CONCAT(`empid`,IF(co > 1,CONCAT('-',`rn`),''),',',`place`,',',`class`) AS 'empid,place,class'
FROM
(SELECT
place,class, IF(#id = empid,#rn := #rn+1, #rn := 1) rn
,#id := empid as empid
,countB.co
FROM TableA
INNER JOIN TableB ON TableA.id = TableB.id
INNER JOIN (SELECT id,COUNT(*) co FROM TableB GROUP BY id) countB ON TableB.id = countB.id
CROSS JOIN (SELECT #id :=0,#rn:=0) t2
ORDER BY empid) t1
| empid,place,class |
| :---------------- |
| ab123-1,SL,A |
| ab123-2,SL,B |
| ab123-3,SL,A |
| gh345,AK,A |
| hj890,K,A |
db<>fiddle here