#select query

[sandeep2363]

Enabling Parallelism for a SQL Query

Enabling Parallelism for a SQL Query

You found a query running on large table, you want to enable parallelism to check its speed after normal execution.

For using the parallelism on SQL Query, you need to explicitly defines hints on the SQL Query for forcefully used the parallel operations.

Two way to be used parallel operation on SQL Query as 1. Parallel Hint 2. Parallel_index Hint

Parallel hint…

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[avhumboldt]

Use Database #1

1. Create database db_name;

2. Create table table_name (

    datatype1 (not null, default value);

    ......

    );

3. Drop table table_name;

4. insert into table_name (elements) values (values);

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<h2>select query</h2>

select * from table_name;

: 테이블 내의 모든 데이터를 불러옴

select data1,... from table_name;

: 테이블 내의 원하는 데이터를 제한해서 불러옴

select * from table_name where 조건( ex> first_name = ‘Anne’);

(‘를 같이 쓰고 싶을때는 \ 를 사용하면 된다.)

and , or 을 같이 사용하여 조건을 덧붙일 수 있다.

null 값인지를 확인하고 싶을때는 “where value is null”

★ Like keyword : LIKE 를 이용하면 ~로 시작하는, 끝나는 등의 조건을 데이터를 검색할 수 있다.(정규표현식 같은 느낌)

ex> select * from table_name where location like ‘%CA’;

: CA로 끝나는 모든 값을 찾는다.

★ >= , <= 와 and 를 이용하면 ~사이의 값들 조건을 가진 데이터만을 추출할 수 있다. 그리고 이러한 역할을 하는 BETWEEN 을 이용하는 방법도 있다.

ex> select drink_name from drink_info where calories between 30 and 60;

★ or 을 이용할 때 조건이 너무 많을 경우

ex> select date_name from black_book where rating IN (’innovative’,’fabulous’,’delightful’,’pretty good’);

이런 식으로 간편하게 표현할 수 있다.

반대로 아닌 조건을 줘야 되는 경우 NOT을 이용하면 된다.

ex>select date_name from black_book where rating NOT IN (’innovative’,’fabulous’,’delightful’,’pretty good’);

[softwaretestingclasses]

SQL SELECT Query - SQL SELECT Statement The SELECT Query the basic query is used to retrieve the selected data from database. This is very powerful and largely used command. The result of the select query is stored in result table which is also called as result-set It’s part of the data manipulation... URL: http://www.softwaretestingclass.com/sql-select-query/

SQL SELECT Query - SQL SELECT Statement The SELECT Query the basic query is used to retrieve the selected data from database. This is very powerful and largely used command. The result of the select query is stored in result table which is also called as result-set It’s part of the data manipulation... URL: http://www.softwaretestingclass.com/sql-select-query/