SQL TEXT Date and set data types in MySQL

The MySQL data table fields must have a data type defined. There are about 25 options, most of which are straightforward, and it's not much of a waste of breath. But there are a few that need to be mentioned.

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: 1999-12-08. You can easily use the date function to get the current system time in this format:

Date ("y-m-d")

Also, you can subtract between the data types to get the difference in the number of days:

$age = ($current _date-$birthdate);

Set set is a useful data type and is somewhat similar to enum enum, except that a set can hold multiple values and an enum can only hold one value. Also, a SET type can have up to 64 predetermined values, whereas an ENUM type can handle up to 65,535 predefined values. And what if you need a collection of more than 64 values? Then you need to define multiple sets to solve the problem together.

Wildcard characters

There are two types of identical characters for SQL: "*" and "%". Used in different situations respectively. For example: If you want to see all of the contents of a database, you can query like this:

SELECT * FROM dbname

WHERE user_id like '% ';

Here, two wildcard characters have been used. Do they mean the same thing? are used to match any of the strings, but they are used in different contexts. "*" is used to match field names, and "%" is used to match field values. Another area that is not easily noticed is that the% wildcard character needs to be used in conjunction with the LIKE keyword.

There is also a wildcard, which is the underscore "_", which means different from the above, is used to match any single character.