Select statement that that counts total number of distinct entries in one table, depending on data from another table
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I have two tables: DATA and USERS

USERS


id----sqft----postal----province----city

1------1------Y7R---------BC----Vancouver

2------2------Y7R---------BC----Vancouver

3------1------L5B---------ON----Toronto

and

DATA

id----uid----power

1-----1------1000

2-----2------1300

3-----1------1500


uid in table DATA matches to id in table USERS

I want to be able to count the the number of distinct uid in DATA where the postal code is Y7R and sqft is 1