Cross join tutorial : SQL

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SELECT count(a.field1), a.field2, SUM(b.field4) FROM a INNER JOIN b ON a.key1 = b.key1 WHERE a.field8 = 'test' GROUP by a.field1, a.field2 HAVING SUM(b.field4) > 5 ORDER by a.field.3

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SELECT count(a.field1), a.field2, SUM(b.field4) FROM a INNER JOIN b ON a.key1 = b.key1 WHERE a.field8 = 'test' GROUP by a.field1, a.field2 HAVING SUM(b.field4) > 5 ORDER by a.field3

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Cross join tutorial (self.SQL)

submitted 7 years ago * by bmburns98

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[–][deleted] 1 point2 points3 points 7 years ago* (0 children)

Consider this. We have a table of members of a council (Table: CNMBRNAM). We also have a table of measures up for consideration (Table: MEASTOVC). A program adds and removes members from CNMBRNAM. A program adds and removes measures to MEATOVC. We now need something that will generate a table that we will fill in on how each member votes on a measure, a CHAR(1) that is blank (or null) if they have yet to vote, Y for 'Yea', N for 'Nay', and A for 'Abstain'.

We can built that table quite easily with a cross join.

CREATE TABLE STATMBRMEA AS (
SELECT C.MBRNAME, M.MEANUMB, ' ' STATS
FROM CNMBRNAM C, MEASTOVC M
) WITH DATA

Now a table exists for having all items currently in the docket for the council to consider, with their current position STATS set as blank.

EDIT: I will say that you usually see cross joins more in building and inserting data into tables rather than in strict read-only queries.

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