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#21
 
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Re: projection with nulls -
03-16-2008
, 05:55 PM
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David Cressey wrote: ... I have always treated GROUP BY and SELECT DISTINCT as providing the functionality that's closest to projection. Some dialects of SQL will indeed eliminate the second tuple if GROUP BY or SELECT DISTINCT are used. ... What is SQL's SELECT but projection? |
The from clause is cartesian product and/or join and/or union (outer join).
THe where clause is restrict.
The group by clause is a curious sort of project that's required for
aggregation.
The having clause is restrict again.
#22
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David Cressey wrote: ... I have always treated GROUP BY and SELECT DISTINCT as providing the functionality that's closest to projection. Some dialects of SQL will indeed eliminate the second tuple if GROUP BY or SELECT DISTINCT are used. ... What is SQL's SELECT but projection? |
The from clause is cartesian product and/or join and/or union (outer join).
THe where clause is restrict.
The group by clause is a curious sort of project that's required for
aggregation.
The having clause is restrict again.
#23
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David Cressey wrote: ... I have always treated GROUP BY and SELECT DISTINCT as providing the functionality that's closest to projection. Some dialects of SQL will indeed eliminate the second tuple if GROUP BY or SELECT DISTINCT are used. ... What is SQL's SELECT but projection? |
The from clause is cartesian product and/or join and/or union (outer join).
THe where clause is restrict.
The group by clause is a curious sort of project that's required for
aggregation.
The having clause is restrict again.
#24
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David Cressey wrote: ... I have always treated GROUP BY and SELECT DISTINCT as providing the functionality that's closest to projection. Some dialects of SQL will indeed eliminate the second tuple if GROUP BY or SELECT DISTINCT are used. ... What is SQL's SELECT but projection? |
The from clause is cartesian product and/or join and/or union (outer join).
THe where clause is restrict.
The group by clause is a curious sort of project that's required for
aggregation.
The having clause is restrict again.
#25
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David Cressey wrote: ... I have always treated GROUP BY and SELECT DISTINCT as providing the functionality that's closest to projection. Some dialects of SQL will indeed eliminate the second tuple if GROUP BY or SELECT DISTINCT are used. ... What is SQL's SELECT but projection? |
The from clause is cartesian product and/or join and/or union (outer join).
THe where clause is restrict.
The group by clause is a curious sort of project that's required for
aggregation.
The having clause is restrict again.
#26
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David Cressey wrote: ... I have always treated GROUP BY and SELECT DISTINCT as providing the functionality that's closest to projection. Some dialects of SQL will indeed eliminate the second tuple if GROUP BY or SELECT DISTINCT are used. ... What is SQL's SELECT but projection? |
The from clause is cartesian product and/or join and/or union (outer join).
THe where clause is restrict.
The group by clause is a curious sort of project that's required for
aggregation.
The having clause is restrict again.
#27
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David Cressey wrote: ... I have always treated GROUP BY and SELECT DISTINCT as providing the functionality that's closest to projection. Some dialects of SQL will indeed eliminate the second tuple if GROUP BY or SELECT DISTINCT are used. ... What is SQL's SELECT but projection? |
The from clause is cartesian product and/or join and/or union (outer join).
THe where clause is restrict.
The group by clause is a curious sort of project that's required for
aggregation.
The having clause is restrict again.
#28
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David Cressey wrote: ... I have always treated GROUP BY and SELECT DISTINCT as providing the functionality that's closest to projection. Some dialects of SQL will indeed eliminate the second tuple if GROUP BY or SELECT DISTINCT are used. ... What is SQL's SELECT but projection? |
The from clause is cartesian product and/or join and/or union (outer join).
THe where clause is restrict.
The group by clause is a curious sort of project that's required for
aggregation.
The having clause is restrict again.
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