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  • 第八章 分组和聚集

    1.基本描述

        本章主要讲解如何对数据进行分组与聚类,以使用户在更高的粒度层次上与数据进行交互。

    2.基本样例

    SELECT open_emp_id FROM account;
    
    SELECT open_emp_id FROM account GROUP BY open_emp_id;
    
    SELECT open_emp_id, COUNT(*) how_many FROM account GROUP BY open_emp_id;
    
    SELECT open_emp_id, COUNT(*) how_many FROM account 
    GROUP BY open_emp_id HAVING COUNT(*) > 4;
    
    SELECT MAX(avail_balance) max_balance, MIN(avail_balance) min_balance, 
    AVG(avail_balance) avg_balance, SUM(avail_balance) tot_balance,
    COUNT(*) num_accounts FROM account WHERE product_cd = 'CHK';
    
    SELECT product_cd, MAX(avail_balance) max_balance, 
    MIN(avail_balance) min_balance, AVG(avail_balance) avg_balance,
    SUM(avail_balance) tot_balance, COUNT(*) num_accts FROM account GROUP BY product_cd;
    
    SELECT account_id, open_emp_id FROM account ORDER BY open_emp_id;
    
    SELECT COUNT(open_emp_id) FROM account;
    
    SELECT COUNT(DISTINCT open_emp_id) FROM account;
    
    SELECT MAX(pending_balance - avail_balance) max_uncleared FROM account;
    
    SELECT product_cd, SUM(avail_balance) prod_balance FROM account GROUP BY product_cd;
    
    SELECT product_cd, open_branch_id, SUM(avail_balance) tot_balance FROM account 
    GROUP BY product_cd, open_branch_id;
    
    SELECT EXTRACT(YEAR FROM start_date) year, COUNT(*) how_many FROM employee 
    GROUP BY EXTRACT(YEAR FROM start_date);
    
    SELECT product_cd, open_branch_id, SUM(avail_balance) tot_balance FROM account
    GROUP BY product_cd, open_branch_id WITH ROLLUP;
    
    SELECT product_cd, SUM(avail_balance) prod_balance FROM account WHERE status = 'ACTIVE' GROUP BY product_cd
    HAVING SUM(avail_balance) >= 10000;
    
    SELECT product_cd, SUM(avail_balance) prod_balance FROM account WHERE status = 'ACTIVE' GROUP BY product_cd
    HAVING MIN(avail_balance) >= 1000 AND MAX(avail_balance) <= 10000; 
    
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  • 原文地址:https://www.cnblogs.com/LuckPsyduck/p/12608261.html
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