Oracle Series: (16) pagination

Review MySQL Paging Use the Limit keyword Querying the top two records in the Users table SELECT * from Users limit 0,2 Or SELECT * from users limit 2; 0 indicates the index number of the first record, and the index number starts at 0 2 indicates a maximum of two records selected Check out the top three records of users SELECT * from Users limit 0,3 Or SELECT * From Users limit 3 Check out the records of users 2nd through 4th SELECT * from Users limit 1, 3;

Review Hibernate paging API Query.setfirstresult (0); Query.setmaxresult (3);

What is rownum, what is the characteristic

1) rownum is a key word dedicated to Oracle

2) rownum with the table, the table died it died, the table in it in

3) RowNum By default, it is not found in the table

4) Only in the SELECT clause, explicitly write out rownum to show

5) RowNum is the number type and the only continuous

6) The minimum value of rownum is 1 and the maximum value is the same as your record number

7) RowNum can also participate in relational operations

* rownum = 1 has value

* RowNum < 5 value

* rownum <=5 has value

* rownum > 2 No value

* RowNum >=2 No value

* rownum <>2 has the same value as RowNum < 2

* RowNum = 2 No value

8) based on rownum characteristics, we usually rownum only for < or <= relational operations

Displays 3-8 records in the EMP table (method One: Use Set subtraction)

Select RowNum "Pseudo-column", emp.* from EMP where Rownum<=8minusselect rownum,emp.* from EMP where rownum<=2;

Displays 2-8 records in the EMP table (way two: using subqueries, using in the FROM clause, emphasis)

Select Xx.*from (select RowNum ids,emp.* from emp where rownum<=8) xx where ids>=2;

Note: Aliases in subqueries are not added "" quotation marks

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displaying 5-9 records in the EMP table

Select Yy.*from (select RowNum ids,emp.* from emp where rownum<=9) Yywhere ids>=5;

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Note: In a project, there may be a real table name after from, or a table name that can be considered as a subquery.

A table to be considered as a real table and a subquery to make a connection query

Oracle Series: (16) pagination