DATABASE | MYSQL | MYSQL INTERVIEW QUESTION AND ANSWERS 7 | WHAT IS DIFFERENCE BETWEEN PRIMARY KEY AND CANDIDATE KEY? | HOW DO YOU GET THE MONTH FROM A TIMESTAMP? | WHAT DO % AND _ MEAN INSIDE LIKE STATEMENT? | IF YOU SPECIFY THE DATA TYPE AS DECIMAL (5,2), WHAT’S THE RANGE OF VALUES THAT CAN GO IN THIS TABLE? | HOW DO YOU GET THE CURRENT DATE IN MYSQL?

Mysql Interview Question and Answers:

31.     what is difference between primary key and candidate key?
      Primary Key
- are used to uniquely identify each row of the table. A table can have only one primary Key.
Candidate Key
- primary key is a candidate key. There is no difference. By common convention one candidate key is designated as a “primary” one and that key is used for any foreign key references.

32.     How do you get the month from a timestamp?
      SELECT MONTH(january_timestamp) from tablename;

33.     What do % and _ mean inside LIKE statement?
      % corresponds to 0 or more characters, _ is exactly one character.

34.     If you specify the data type as DECIMAL (5,2), what’s the range of values that can go in this table?
      999.99 to -99.99. Note that with the negative number the minus sign is considered one of the digits.

35.     How do you get the current date in Mysql?
      SELECT CURRENT_DATE();