Get Maximum value of a column in mysql DB

Question

My DB table column values are

tenant_ id  group_id
2           2-100
2           2-111
1           1-222
1           1-888
2           2-999 
2           2-1000

Query :

select max(group_id) from prospect_group where tenant_id=2

I have used the above query to get the max value for tenant_id=2 but it returns the value as 999 instead of 1000. How to get 1000 as the max value.??? Can anyone help me..???

Answer 1

You need to have GROUP BY clause

SELECT tenant_ID, MAX(CAST(group_ID AS SIGNED))
FROM tableName
-- WHERE  tenant_id=2 -- uncomment this if you select only for specific tenant_ID
GROUP BY tenant_ID

try it by replacing to an empty char.

SELECT tenant_ID, 
       MAX(CAST(REPLACE(group_ID, CONCAT(tenant_ID, '-'), '')  AS SIGNED)) maxGID
FROM tableName
-- WHERE  tenant_id=2 -- uncomment this if you select only for specific tenant_ID
GROUP BY tenant_ID

SQLFiddle Demo

Answer 2

You need to add GROUP BY clause.

select max(group_id) from prospect_group where tenant_id=2 group by tenant_ id