Adding entries from multiple MySQL tables using one single SQL join statement, but only if there are entries available in the second table -


using 1 single sql query join: how can add entries second table if there corresponding entry available?

project                                source  description   |  source                source_id   |  value ----------------------------           -------------------------------- project 1     |  1                     1           |  additional info 1 project 2     |  null

when type

select project.description, source.value project, source project.source = source.source_id , project.description = "project 1";

as desired receive 

project 1   |   additional info 1

however when replace project 1 project 2 in last line, won't result, because project.source null. possible use single sql query outputs this? 

project 2   |   null

i´m looking query covers both cases.

any ideas?

you can use left join on project table make sure all projects appear in result set if have no matching value in source table. projects project table not match have null value.

select project.description description, source.value value project left join source on project.source = source.source_id

output:

+--------------+--------------------+ | description  |       value        | ---------------+--------------------+ |  project 1   |  additional info 1 | |  project 2   |  null              | +--------------+--------------------+

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