Implementation of MySQL non-repeated Query

Non-repeated query in MySQL is an important query method in MySQL. The following describes how to implement non-repeated query in MySQL.

No duplicate query in MySQL is a unique query, that is, the query results that meet the conditions but are different from each other. First, let's look at an example:

 
 

  
  
select title from employee_data;  
  
  
   
  
  
+----------------------------+  
  
  
| title                      |  
  
  
+----------------------------+  
  
  
| CEO                        |  
  
  
| Senior Programmer          |  
  
  
| Senior Programmer          |  
  
  
| Web Designer               |  
  
  
| Web Designer               |  
  
  
| Programmer                 |  
  
  
| Programmer                 |  
  
  
| Programmer                 |  
  
  
| Programmer                 |  
  
  
| Multimedia Programmer      |  
  
  
| Multimedia Programmer      |  
 
 

...

In the preceding example, We query the title (title) in the employee_data table and note that many of the results are duplicated. If we want to get a non-repeated result, we can use the mysql keyword-DISTINCT.

 
 

  
  
select DISTINCT title from employee_data;  
  
  
   
  
  
+----------------------------+  
  
  
| title                      |  
  
  
+----------------------------+  
  
  
| CEO                        |  
  
  
| Customer Service Manager   |  
  
  
| Finance Manager            |  
  
  
| Marketing Executive        |  
  
  
| Multimedia Programmer      |  
  
  
| Programmer                 |  
  
  
| Senior Marketing Executive |  
  
  
| Senior Programmer          |  
  
  
| Senior Web Designer        |  
  
  
| System Administrator       |  
  
  
| Web Designer               |  
  
  
+----------------------------+  
  
  
11 rows in set (0.00 sec)  
  
  
 
 
 

In this way, all the company's job categories can be listed without review. In addition, we can also use DISTINCT and ordber by to sort unique (non-duplicated) results, for example:

 
 

  
  
select DISTINCT age from employee_data  
  
  
ORDER BY age;  
  
  
   
  
  
+------+  
  
  
| age  |  
  
  
+------+  
  
  
|   25 |  
  
  
|   26 |  
  
  
|   27 |  
  
  
|   28 |  
  
  
|   30 |  
  
  
|   31 |  
  
  
|   32 |  
  
  
|   33 |  
  
  
|   34 |  
  
  
|   35 |  
  
  
|   36 |  
  
  
|   43 |  
  
  
+------+  
  
  
12 rows in set (0.00 sec)  
  
  
 
  
  
   
  
  
 
 
 

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