查询错误，列ambiguos

Question

查询会生成错误消息。为什么会这样？如何更正查询？

SELECT NAME, DATE
FROM LETTER, LANGUAGE, CITY
WHERE LANGUAGE = LANG_ID
AND PLACE_SENT = CITY_ID ;

错误：

  

无法执行查询：1052：where子句中的列'LANGUAGE'   含糊不清

Answer 1

1st：这意味着两个表中都会显示LANGUAGE列。您需要指定要获得的列。

第二次：您需要在table后使用column name名称，以避免列名ambiguous error

SELECT LETTER.NAME, LETTER.DATE
FROM LETTER , LANGUAGE, CITY
WHERE LETTER.LANGUAGE = LANGUAGE.LANG_ID
AND LETTER.PLACE_SENT = CITY.CITY_ID ;

Answer 2

因此LANGUAUGE列存在于多个表中。因此，您需要澄清要从中选择此列的表。请在where子句中添加表名

SELECT LETTER.NAME, LETTER.DATE
FROM LETTER , LANGUAGE, CITY
WHERE LETTER.LANGUAGE = LANGUAGE.LANG_ID
AND LETTER.PLACE_SENT = CITY.CITY_ID ;

Answer 3

我必须猜测：

SELECT NAME, DATE
FROM LETTER, LANGUAGE, CITY
WHERE LETTER.LANGUAGE = LANG_ID
AND PLACE_SENT = CITY_ID ;

或

SELECT NAME, DATE
FROM LETTER, LANGUAGE, CITY
WHERE CITY.LANGUAGE = LANG_ID
AND PLACE_SENT = CITY_ID ;

或

SELECT NAME, DATE
FROM LETTER, LANGUAGE, CITY
WHERE LANGUAGE.LANGUAGE = LANG_ID
AND PLACE_SENT = CITY_ID ;

或

SELECT NAME, DATE
FROM LETTER, LANGUAGE, CITY
WHERE LANGUAGE.ID = LANG_ID
AND PLACE_SENT = CITY_ID ;

可能会解决您的问题。

Answer 4

有名称为LANGUAGE的表，属性名称为LANGUAGE。 我在你的查询中用粗体文字标记了它们。另外请将where子句提及为 TABLE.Attribute 看下面

选择姓名，日期 来自信件， LANGUAGE ，CITY 在哪里 表。 LANGUAGE = LANG_ID AND 表。 PLACE_SENT = CITY_ID;