mysql - Showing empty values in join | Sales value - category - 


select    cat_tbl.id_cat,     cat_tbl.name,     sum(expences.price) pricetotal cat_tbl   join  expences on cat_tbl.id_kat= expences.category  group     cat_tbl.id_cat,      cat_tbl.name

result 

+------+--------------+--------+ | name | pricetotal   | id_cat | +------+--------------+--------+ | cat1 |      1031.40 |      1 | | cat2 |       200.88 |      2 | | cat4 |        46.44 |      4 | | cat5 |       223.76 |      5 | +------+--------------+--------+

the thing have more 4 categories, tried different joins won't show categories 1-7 null values pricetotal .

i don't know how make such

+------+--------------+--------+ | name | pricetotal   | id_cat | +------+--------------+--------+ | cat1 |      1031.40 |      1 | | cat2 |       200.88 |      2 | | cat3 |         0    |      3 | | cat4 |        46.44 |      4 | | cat5 |       223.76 |      5 | | cat6 |       0      |      6 | | cat7 |       0      |      7 | +------+--------------+--------+

2 options left join:

select    cat_tbl.id_cat,     cat_tbl.name,     sum(expences.price) pricetotal cat_tbl   left join  expences       on cat_tbl.id_kat= expences.category group     cat_tbl.id_cat,      cat_tbl.name

or:

select cat.id_cat, cat.name,        coalesce(exp.tot, 0) pricetotal cat_tbl cat left join ( select x.category, sum(x.price) tot expences x group x.category ) exp on cat.id_cat = exp.category

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