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

Query according to specific conditions

WEHRE LIKE BETWEEN IN ON OR.

UNION keyword

Join multiple tables together for row-level processing

SELECT expression1, expression2,... Expression_n

FROM tables

[WHERE conditions]

UNION [ALL | DISTINCT]

SELECT expression1, expression2,... Expression_n

FROM tables

[WHERE conditions]

Parameter description

Expression1, expression2,... Expression_n: the column to retrieve.

Tables: the data table to retrieve.

WHERE conditions: optional, search condition.

DISTINCT: optionally, delete duplicate data in the result set. By default, the UNION operator has removed duplicate data, so the DISTINCT modifier has little effect on the result.

ALL: optional, returns all result sets, including duplicate data.

Sort ORDER BY

Grouping GORUP BY+HAVING

Filter DISTINCT

Join query SQL92/SQL99

The only difference: external connection

Left outside connection LEFT JOIN

Right external connection RIGHT JOIN

Paging query

Original

SELECT FROM

SELECT ROWNUM NUT,T. FROM

(SELECT FROM EMP ORDER BY SAL) T WHERE ROWNUM5

Now

SELECT FROM EMP LIMIT 1,10

Where SELECT * FROM EMP LIMIT N M; N represents the starting position M represents several records in a page.

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