我有一张表格，里面有一组数据，我想使用Mysql显示它的特定记录：

Question

以下是表格：抱歉，无法在此处正确描述表格。现在

Id Date1 Rank1 date2  Rank2 

100 1/1/01 1  1/2/01  1 

100 1/2/01 1  1/3/01  1 

100 1/3/01 1  1/5/01  4 

，我希望看到的结果，其中排名有所变化，但日期1应显示从排名= 1开始的日期， 的输出是这样的：

Id Date1 Rank1  date2 Rank2 

100 1/1/01  1  1/5/01  4 

谁能请让我知道如何去做这件事在MYSQL？我想过使用SQL游标。是否有另一种方式？

Answer 1

我将创建一个存储过程和光标通过每个记录进行迭代。

我的存储过程将如下所示：

CREATE PROCEDURE `GetChangedRank`() 
BEGIN 

# Variables containing the final result 
DECLARE ID INTEGER; 
DECLARE DATE1 DATE; 
DECLARE Rank1 INTEGER; 
DECLARE DATE2 DATE; 
DECLARE Rank2 INTEGER; 

DECLARE ROWNUM INTEGER DEFAULT 0; 

# Temporary variables to store values of each row. 
DECLARE v_finished INTEGER DEFAULT 0; 
DECLARE ID_VALUE INT; 
DECLARE DATE1_VALUE DATE; 
DECLARE Rank1_VALUE INT; 
DECLARE DATE2_VALUE DATE; 
DECLARE Rank2_VALUE INT; 

# testtable is the table that contains data 

DECLARE RECORDS_CURSOR CURSOR FOR SELECT * FROM testtable; 

# To check if we reached the end of the result set 
DECLARE CONTINUE HANDLER FOR NOT FOUND SET v_finished = 1; 

# Open cursor 
OPEN RECORDS_CURSOR; 

# Loop to fetch one row at a time 
get_records: LOOP 
# Fetch row values to different variables 
FETCH RECORDS_CURSOR INTO ID_VALUE, DATE1_VALUE, Rank1_VALUE, DATE2_VALUE, Rank2_VALUE 
# To track the row number 
SET ROWNUM = ROWNUM + 1; 

# Quit the loop when the end of resultset is reached. 
IF v_finished = 1 THEN 
LEAVE get_records; 
END IF; 

# Assign the first row values to the final values. Date2 and Rank2 will be updated when the rank is changed. 
IF ROWNUM = 1 THEN 
    BEGIN  
     SET ID = ID_VALUE; 
     SET DATE1 = DATE1_VALUE; 
     SET Rank1 = Rank1_VALUE; 
     SET DATE2 = DATE2_VALUE;  
     SET Rank2 = Rank2_VALUE;  
    END; 
ELSE 
    BEGIN 
     # Date2 and Rank2 is updated with the row values as the rank is changed. 
     IF Rank1_VALUE != Rank2_VALUE THEN 
      BEGIN 
       SET DATE2 =DATE2_VALUE; 
       SET Rank2 = Rank2_VALUE; 
      END;  
      END IF; 
    END;  
END IF; 

END LOOP get_records; 

# Select the final values 
SELECT ID, DATE1, Rank1, DATE2, Rank2; 

# Close cursor 
CLOSE RECORDS_CURSOR; 

END 

一旦程序被创建，您可以运行此程序如下

CALL GetChangedRank; 

Answer 2

这是你想要的吗？

SELECT * FROM <table name> 
WHERE Rank1 <> Rank2 

Answer 3

试试这个嵌套查询

Select Id, (select Date1 from TableName group by Rank1) as Date1, Rank1, Date2, Rank2 from TableName where Rank1<>Rank2;