SQL Optimization （SQL 优化）
1) * && field
SELECT * from sys_user
SELECT USER_ID, USER_NAME, EMAIL FROM SYS_USER;
栗子：
48.664s 142877rows
6.194s 142877rows
2）UNION && UNION ALL
SELECT USER_ID, USER_NAME, EMAIL FROM SYS_USER
UNION
SELECT USER_ID, USER_NAME, EMAIL FROM SYS_USER ORDER BY USER_ID;
SELECT USER_ID, USER_NAME, EMAIL FROM SYS_USER
UNION ALL
SELECT USER_ID, USER_NAME, EMAIL FROM SYS_USER ORDER BY USER_ID;
3） IN （1, ......., 1000, ..... 2000）j假设条件过多，拆分，UNION ALL
SELECT * FROM sys_user WHERE USER_ID IN (1, 2, 3, 4, 2000);
SELECT * FROM sys_user WHERE USER_ID IN (1, 2, 3, 4, 1000)
UNION ALL
SELECT * FROM sys_user WHERE USER_ID IN (1001, 2000);
4）batch insert （limited 500 rows）
INSERT INTO SYS_USER (USER_ID, USER_NAME) VALUES (1, ZWF), (2, 005129), (500, 13805029595);
5）limit
SELECT * FROM SYS_USER LIMIT 1;
6）分页
MYSQL分页：
SELECT column1, column2, ...FROM table_name ORDER BY column_name LIMIT offset, count;
SELECT * FROM sys_user ORDER BY user_id LIMIT 0, 10;
SELECT * FROM sys_user ORDER BY user_id LIMIT 10, 10;
ORACLE分页：
SELECT * FROM (
SELECT a.*, ROWNUM rnum FROM (
SELECT * FROM your_table ORDER BY some_column
) a
WHERE ROWNUM <= :end_row
)
WHERE rnum > :start_row;
7）EXPLAIN
SELECT id FROM logic_case_detail;
EXPLAIN SELECT id FROM logic_case_detail;
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