Shulou(Shulou.com)06/01 Report--

For a sql statement, many keywords SELECT FROM JOIN WHERE GROUP BY HAVING ORDER BY LIMIT are used, which cannot be repeated with these keywords when naming. The following describes the meaning respectively.

1Direct select query statement command line

SELECT is followed by a list of comma-separated columns or asterisks (*), indicating that all columns are to be returned

2Gen from command line

FROM specifies the table or view to query the data.

3JOIN command line

Get data from other tables based on certain connection conditions.

4judgment of where condition

WHERE filters the rows in the result set.

5Graup BY grouping

Combine a set of rows into small groups and apply an aggregate function to each small packet

6HAVING command line

Filters are based on subgroups defined by the GROUP BY clause

7 order BY flashback positive order

Specifies the list of columns used for sorting

8. Limit limits the number of items.

LIMIT limits the number of rows returned

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