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Specifying the columns you want also allows you to create indexes that have the data you need as part of the index. Select “a” from “b” where “c” = 1; With a
by rubyist5eva 6y ago
Specifying the columns you want also allows you to create indexes that have the data you need as part of the index.
Select “a” from “b” where “c” = 1;
With a composite index on c and a allows you to fetch everything you need without even looking at the table.
- jve 6y agoAnd this is SO important. Even if this is the sole reason why * should be considered bad. In some cases on big databases, adding covering index is the way to make your apication perform well, by eliminating those table lookups.