Prior to retrieve data
5.3 to retrieve data
** 1. Select data for selecting tables, columns in the view.
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for inserting into the structure of the table and the specified data into the new table.
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from the specified data source.
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Where data retrieval for screening.
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group by grouping search results display.
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having: data lines for screening the query result from the use of the packet group by clause
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order by ordering for the result set.
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Column alias: as;
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Show unique record: distinct;
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Fuzzy query: like;
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Any number of characters:%;
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Any one character: _;
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A data value matches a set of targets: IN;
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Results between the two values: between ... and ...;
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Empty: is null; **
Logic screening
- Table connection:
Use join connection:
En:
En equivalent:
Non-equivalent connection:
The connector itself
Left outer join
Right outer join
Multi-line single row subqueries
Single-line multiple-column query
Multi-line multiple-column query
Correlated subquery
Using a subquery in the FROM clause
Use WITH clause subquery
Hierarchical queries
UNION：
INTERSECT：
MINUS
