SQLTEXTDATE and SET data type in MySQL _ MySQL

The SQLTEXTDATE and SET data types in MySQL data tables must have a data type defined. There are about 25 options, most of which are straightforward, so there is not much to worry about. But there are a few things to mention.

TEXT is not a data type, although it may be said in some books. It should actually be "long varchar" or "MEDIUMTEXT ".

The format of the DATE data type is YYYY-MM-DD, for example. You can easily use the date function to obtain the current system time in this format:

Date ("Y-m-d ")

In addition, subtraction can be performed between DATA types to obtain the time difference days:

$ Age = ($ current_date-$ birthdate );

SET is a useful data type. it is similar to ENUM, except that SET can save multiple values while ENUM can only save one value. In addition, the SET type can have up to 64 predefined values, while the ENUM type can process up to 65,535 predefined values. What if we need a set with more than 64 values? In this case, you need to define multiple sets to solve this problem together.

Wildcard
There are two types of SQL configuration characters: "*" and "% ". In different cases. For example, if you want to view all the database content, you can query it like this:

SELECT * FROM dbname

WHERE USER_ID LIKE '% ';

Here, both wildcards are used. They mean the same ?? They are used to match any string, but they are used in different contexts. "*" Is used to match the field name, while "%" is used to match the field value. The wildcard "%" must be used with the LIKE keyword.

Another wildcard is the underscore "_", which represents a different meaning from the above and is used to match any single character.