Introduction to MySQL <> and <=> operators

<> Operator

Function: Indicates not equal to.

Note: It has the same function as the “!=” operator, but “<>” is less readable.

### To query non-Han users, the following two statements have the same effect.
> SELECT * FROM user WHERE nation != "汉族";
> SELECT * FROM user WHERE nation <> "Han";

<=> Operator

Function: Safety is equal to

Note: It integrates the functions of the "=" operator and the IS keyword, and can determine both NULL and basic data types. But in comparison, “<=>” is less readable.

From the following SQL statement, we can see that the "=" operator and the IS keyword cannot be used interchangeably. The "=" operator can only determine basic data types, and the IS keyword can only determine NULL.

The "<=>" operator can be used in relatively few scenarios. It can basically only be used for search conditions. There is no need to determine whether a search condition is NULL or a basic data type.

### Query users who have not filled in their gender. The following statements have the same effect> SELECT * FROM user WHERE sex IS NULL;
> SELECT * FROM user WHERE sex <=> NULL;
 
### Query male users. The following statements have the same effect> SELECT * FROM user WHERE sex = "男";
> SELECT * FROM user WHERE sex <=> "male";

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