SQL JOIN error in vb.net

Question

I have this sql string:

Dim sqlQuery As String = "SELECT TOP 1 ID, FName, FoodGroup, Calories, Protein, Carbohydrates, Fat, category.ID" &
        " FROM food where Protein<='" & txtProt.Text.ToString() & "' and FoodGroup = 4 " & "and category.ID = 1 " & "JOIN foodCategory ON food.ID = foodCategory.Food_ID" & "JOIN category ON foodCategory.Category_ID = category.ID " & "ORDER BY NEWID() "

What i want to do is this: I want to type the value "FName" from table "food" to an textBox where the "ID" field of table "category" is 1.

I have 3 tables. The first is table food, the second one is table category and the third one is foodCategory. The table foodCategory has the ID's from the first 2 tables to a one-to-many relationship. I get the following error : Incorrect syntax near JOIN. What do i do wrong?

Answer 1

如果查询不正确，则必须在FROM子句中设置JOIN，而不是在WHERE子句中设置JOIN。

Answer 2

Try the following query

dim sqlQuery As String 
sqlQuery = "SELECT TOP 1 ID, FName, FoodGroup, Calories, Protein, " & _
           "Carbohydrates, Fat, category.ID " &_
           "FROM food JOIN foodCategory ON " & _
           "food.ID = foodCategory.Food_ID JOIN category ON " & _
           "foodCategory.Category_ID = category.ID " & _
           "where Protein<='" & txtProt.Text.ToString() & "' and " & _
           "FoodGroup = 4 and category.ID = 1 " & _
           "ORDER BY NEWID() "

Furthermore you should have look at Parameter as your code is very vulnerable to SQL injection !

Answer 3

It's probably your concatenation:

... foodCategory.Food_ID" & "JOIN category ...

would evaluate to

foodCategory.Food_IDJOIN category

Answer 4

您的JOIN必须在WHERE子句之前：

 " FROM food" & " JOIN foodCategory ON food.ID = foodCategory.Food_ID" & "JOIN category ON       foodCategory.Category_ID = category.ID " & " WHERE Protein<='" & txtProt.Text.ToString() & "'  and FoodGroup = 4 " & "and category.ID = 1 " & " ORDER BY NEWID() ";