在INNER JOIN中使用列別名

Question

嘗試運行以下查詢時，收到錯誤消息“'on子句'中的未知列'YahrzeitName'”：

SELECT 
concat(yahrzeit.firstName, ' ', yahrzeit.middleName, ' ', yahrzeit.lastName) 
AS 'YahrzeitName', 

concat(yahrzeit.gregorianYear, '-', yahrzeit.gregorianMonthNum, '-', yahrzeit.gregorianDay) 
AS Date,

tbldecedent.Name

FROM yahrzeit INNER JOIN tbldecedent 
ON YahrzeitName = tbldecedent.Name

Answer 1

您不能在join語句中使用列別名，而是用完整的表達式替換別名：

SELECT 
    concat(yahrzeit.firstName, ' ', yahrzeit.middleName, ' ', yahrzeit.lastName) AS `YahrzeitName`,
    concat(yahrzeit.gregorianYear, '-', yahrzeit.gregorianMonthNum, '-', yahrzeit.gregorianDay) AS `Date`,
    tbldecedent.Name
FROM yahrzeit 
INNER JOIN tbldecedent
ON concat(yahrzeit.firstName, ' ', yahrzeit.middleName, ' ', yahrzeit.lastName) = tbldecedent.Name