Q1、第一次工作寫命令時，寫了一個把一個表的數據插入到另一個表中，運行時命令長時間處於執行狀態。
A、第一次處理數據庫大量數據，長時間按運行屬於正常現象，這與學校中的小數據不同。
Q2、如何查詢數據庫中某個時間段內的數據。
A2、
//今天
select * from 表名 where to_days(時間字段名) = to_days(now());
//昨天
SELECT * FROM 表名 WHERE TO_DAYS( NOW( ) ) - TO_DAYS( 時間字段名) <= 1
//近7天
SELECT * FROM 表名 where DATE_SUB(CURDATE(), INTERVAL 7 DAY) <= date(時間字段名)
//近30天
SELECT * FROM 表名 where DATE_SUB(CURDATE(), INTERVAL 30 DAY) <= date(時間字段名)
//本月
SELECT * FROM 表名 WHERE DATE_FORMAT( 時間字段名, '%Y%m' ) = DATE_FORMAT( CURDATE( ) , '%Y%m' )
//上一月
SELECT * FROM 表名 WHERE PERIOD_DIFF( date_format( now( ) , '%Y%m' ) , date_format( 時間字段名, '%Y%m' ) ) =1
//查詢本季度數據
select * from `ht_invoice_information` where QUARTER(create_date)=QUARTER(now());
//查詢上季度數據
select * from `ht_invoice_information` where QUARTER(create_date)=QUARTER(DATE_SUB(now(),interval 1 QUARTER));
//查詢本年數據
select * from `ht_invoice_information` where YEAR(create_date)=YEAR(NOW());
//查詢上年數據
select * from `ht_invoice_information` where year(create_date)=year(date_sub(now(),interval 1 year));
//查詢當前這周的數據
SELECT name,submittime FROM enterprise WHERE YEARWEEK(date_format(submittime,'%Y-%m-%d')) = YEARWEEK(now());
//查詢上周的數據
SELECT name,submittime FROM enterprise WHERE YEARWEEK(date_format(submittime,'%Y-%m-%d')) = YEARWEEK(now())-1;
//查詢上個月的數據
select name,submittime from enterprise where date_format(submittime,'%Y-%m')=date_format(DATE_SUB(curdate(), INTERVAL 1 MONTH),'%Y-%m')
select * from user where DATE_FORMAT(pudate,'%Y%m') = DATE_FORMAT(CURDATE(),'%Y%m') ;
select * from user where WEEKOFYEAR(FROM_UNIXTIME(pudate,'%y-%m-%d')) = WEEKOFYEAR(now())
select * from user where MONTH(FROM_UNIXTIME(pudate,'%y-%m-%d')) = MONTH(now())
select * from user where YEAR(FROM_UNIXTIME(pudate,'%y-%m-%d')) = YEAR(now()) and MONTH(FROM_UNIXTIME(pudate,'%y-%m-%d')) = MONTH(now())
select * from user where pudate between 上月最后一天 and 下月第一天
//查詢當前月份的數據
select name,submittime from enterprise where date_format(submittime,'%Y-%m')=date_format(now(),'%Y-%m')
字段為date類型
Q3、刪除表中數據
A3、
1、delete語法：DELETE FROM 表名稱 WHERE 列名稱 = 值。
2、刪除所有行：可以在不刪除表的情況下刪除所有的行。這意味着表的結構、屬性和索引都是完整的：DELETE FROM table_name。
3、 用於清空某表的數據 且讓自增的id重新從0開始truncate table 你的表名
Q4、查詢規定幾行
A4、
mysql> SELECT * FROM table LIMIT 5,10; // 檢索記錄行 6-15
mysql> SELECT * FROM table LIMIT 5; //檢索前 5 個記錄行