蚂蚁 sql tel 重复

1. 1 基础去重查询（推荐）
   
2. sql
   
3. SELECT DISTINCT tel AS '电话号码'
   
4. FROM rental_information;
   
5. 2 排序去重查询
   
6. sql
   
7. SELECT DISTINCT tel AS '电话号码'
   
8. FROM rental_information
   
9. ORDER BY tel;
   
10. 3 统计出现次数
    
11. sql
    
12. SELECT
    
13.     tel AS '电话号码',
    
14.     COUNT(*) AS '出现次数'
    
15. FROM rental_information
    
16. GROUP BY tel
    
17. ORDER BY tel;
    
18. 4 有效号码筛选
    
19. sql
    
20. SELECT DISTINCT tel AS '电话号码'
    
21. FROM rental_information
    
22. WHERE tel IS NOT NULL
    
23.   AND tel != ''
    
24.   AND tel REGEXP '^1[3-9][0-9]{9}
    
25. 
    
26. 
    
27. ORDER BY tel;

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