Oracle use function in query

1. Using character functions in queries

1. Demand

Query the employee's birthday in the employee information table, and get the birthday according to the employee's ID number.

2. Examples

1. SQL>select*from users;
3. ID NAME CARDID DEPTNO REGDATE AGE
4. -------------------------------------------------------------------------
5. 1 abc 123456199205050105-5月-1718
7. SQL>select substr(cardid ,7,8)from users;
9. SUBSTR(CARDID,7,
10. ----------------
11. 19920505

3. Demand

Replace all department number 01 with information technology

4. Examples

1. SQL>select replace(deptno ,'01','信息技术')from users;
3. REPLACE(DEPTNO,'01','信息技术')
4. --------------------------------------------------------------------------------
5. 信息技术

 

2. Use numeric type functions in queries

1. Demand

Take the remainder of the age field in the employee information table and 10

2. Code

1. SQL>select mod(age,10)from users;
3. MOD(AGE,10)
4. -----------
5. 8

 

3. Use date functions in queries

1. Demand

The year the employee was hired

Find out the information of employees who joined in May

1. SQL>select extract(year from regdate)from users;
3. EXTRACT(YEARFROMREGDATE)
4. ------------------------
5. 2017
7. SQL>select*from users where extract(month from regdate)=5;
9. ID NAME CARDID DEPTNO REGDATE AGE
10. -------------------------------------------------------------------------
11. 1 abc 123456199205050105-5月-1718