將兩個字段（彼此依賴）相互關聯到另一個表中的相同字段

Question

SELECT RECIPE.PRODUCTNUMBER, RECIPE.COMPONANTNUMBER, 
  RECIPE.COMPQUANTITY, RECIPE.COMPSEQNO, ITMMSTR.ITEMDESCRIPTION 
FROM RECIPETABLE RECIPE, ITEMMASTERTABLE ITMMSTR 
WHERE RECIPE.PRODUCTNUMBER=ITMMSTR.ITEMNUMBER

Answer 1

聽起來您需要兩次加入ITEMMASTERTABLE ：

SELECT
    r.PRODUCTNUMBER, r.COMPONANTNUMBER, r.COMPQUANTITY, r.COMPSEQNO,
    p.ITEMDESCRIPTION as ProductDescription, i.ITEMDESCRIPTION as ComponentDescription
FROM RECIPETABLE r, ITEMMASTERTABLE p /*product*/, ITEMMASTERTABLE i /*item*/
WHERE
        r.PRODUCTNUMBER = p.PRODUCTNUMBER
    AND r.COMPONANTNUMBER = i.ITEMNUMBER

當然，您將需要使用ANSI連接語法：

SELECT
    r.PRODUCTNUMBER, r.COMPONANTNUMBER, r.COMPQUANTITY, r.COMPSEQNO,
    p.ITEMDESCRIPTION as ProductDescription, i.ITEMDESCRIPTION as ComponentDescription
FROM
    RECIPETABLE r
    INNER JOIN ITEMMASTERTABLE p /*product*/,
        ON r.PRODUCTNUMBER = p.PRODUCTNUMBER
    INNER JOIN ITEMMASTERTABLE i /*item*/
        ON r.COMPONANTNUMBER = i.ITEMNUMBER