Hong asked 11 years ago
select_command = select concat(p.proj_id,'-',cabs.cab_id) as 'key',
FROM projects p
LEFT JOIN cabs ON p.proj_id = cabs.proj_id_f
Above is my sql command. I want to have a composite key with two colums from different tables. Key is empty when there is no cabs.cab_id in a line
How can I fix this or how can I have a unique key?
1 Answers
Abu Ghufran answered 11 years ago
Hello,
You can use IFNULL() for blank left join table values.
select concat(p.proj_id,'-', IFNULL(cabs.cab_id,0) ) as 'key', ……
Also, You need to write custom on_update, on_insert. on_delete as based DML as only for single tables.
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