join - What is the difference between these two MySQL queries? - 


select count( companyid ) companies  left join cities on cities.cityid = companies.cityid group companies.companyid;

vs

select count( companyid ) cities  left join companies on cities.cityid = companies.cityid group companies.companyid;

what difference?

in first query left table companies , in second query cities.

the left join keyword returns rows left table (table_name1), if there no matches in right table (table_name2).

first query

the left join keyword returns rows companies table , if there no matches in cities table

second query

the left join keyword returns rows cities table , if there no matches in companies table

visual representation of sql joins


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