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我有一个 SQL 表，其列是 State_Code、School_Code 和 School_Type。

样本数据：

State_Code    School_Code     School_Type
 01            01014874        1
 01            01018790        2
 1             10189900        1
 1             10277689        1

*（注：School_Code 的第 1 和第 2 位是实际的州代码，而第 3 和第 4 位是该特定州的 District_Code）*

现在，如果我触发这个查询：

Select COUNT(School_Code) from Table1 where State_Code='1'+0;

它将返回该州的学校数量，代码为“1”；即4 ;

但是，如果我想检索一个州 DISTRICT-WISE 的学校数量；我会触发这个查询：

Select State_Code,SUBSTRING(School_Code,3,2) AS District_Code,COUNT(School_Code) AS Number_of_Schools_In_District FROM Table1 GROUP BY State_Code+0;

这个查询返回我这个输出：

State_Code     District_Code      Number_of_Schools_In_District
   01               01                         2
   1                18                         1
   1                27                         1

但正确的输出是：

State_Code     District_Code      Number_of_Schools_In_District
   01               01                         3
   1                02                         1

这是由于用户在 SQL 表中为 School_Code 列输入的数据不正确。状态“1”和“01”实际上是相同的状态，即“01”。但是由于第 3 行和第 4 行的 School-Code 不是以“0”开头，这会导致输出中的错误行为。

所以要解决这个问题，我将不得不使用这个逻辑：

*If number of characters in State_Code is 1 and School_Code does not start with '0', then a '0' should be prefixed to the School_Code value to get the correct District_Code value.*

我试过这个：

Select State_Code,SUBSTRING(School_Code,3,2) AS District_Code,COUNT(School_Code) AS     Number_of_Schools_In_District FROM Table1 WHERE IF CHARACTER_LENGTH(State_Code)=1 AND School_Code NOT LIKE '0%' THEN REPLACE(School_Code,School_Code,CONCAT(0,School_Code)) END IF GROUP BY State_Code+0, SUBSTRING(School_Code,3,2)+0;

我的期望是，如果 State_code 中的任何值是单个数字并且其相应的学校代码不以“0”开头，那么这将在其上附加“0”，然后计算取第 3 位和第 4 位数字的学区代码。但这不会发生。我仍然得到错误。

Note: I don't want to update original SQL table values.

任何帮助将不胜感激。提前致谢！

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1 回答 1

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试试下面的查询

Select State_Code, IF(CHARACTER_LENGTH(State_Code)=1, SUBSTRING(School_Code,2,2), SUBSTRING(School_Code,3,2)) AS District_Code,COUNT(School_Code) AS     Number_of_Schools_In_District FROM Table1 WHERE GROUP BY State_Code+0, SUBSTRING(School_Code,3,2)+0;
于 2013-03-29T12:32:00.653 回答