基于同一张表获取 3 列左连接

Question

I have 3 column here in tblItem

• purchase
• stock
• calculate

and this 3 column have to join with tblMeasurement

• name

I have tried this, but when I display 3 columns show the same all.

SQL

$sql         = "SELECT A.itemID, A.categoryID, A.purchaseMeasurementID, A.stockMeasurementID, A.calculationMeasurementID, A.itemName, B.itemCategoryName, C.measurementName
                FROM tblPurItem A
                LEFT JOIN tblPurItemCategory B
                ON A.categoryID = B.itemcategoryID
                LEFT JOIN tblPurMeasurement C
                ON A.purchaseMeasurementID= C.measurementID";

As you see my sql above, it has join only for purchaseMeasurementID. How do I join stockMeasurementID and calculationMeasurementID based on also tblPurMeasurement? Is there any missing here?

Answer 1

Try using this subquery instead.

SELECT A.itemID, A.categoryID, A.purchaseMeasurementID, A.stockMeasurementID, A.calculationMeasurementID, A.itemName
    , (select B.itemCategoryName from tblPurItemCategory B where A.categoryID = B.itemcategoryID limit 1) as itemCategoryName
    , (select C.measurementName from tblPurMeasurement C where A.purchaseMeasurementID= C.measurementID limit 1) as purchasemeasurementName
    , (select C.measurementName from tblPurMeasurement C where A.stockMeasurementID= C.measurementID limit 1) as stockmeasurementName
    , (select C.measurementName from tblPurMeasurement C where A.calculationMeasurementID= C.measurementID limit 1) as calculationmeasurementName
FROM tblPurItem A