关于SQL View，我有些困惑

Question

I have these tables:

• BRANCH (Bno, Street, Area, City, Pcode, Tel_No, Fax_No)
• STAFF (Sno, Fname, Lname ,Address ,Tel_No ,Position, Sex, DOB, Salary, NIN, Bno)
• PROPERTY_FOR_RENT (Pno, Street, Area, City, Pcode, Type, Rooms, Rent, Ono, Sno, Bno)

A view BranchStats ( Bno, NumStaff, NumProps ) is to be created that, for any branch, indicates the number of staff members employed and the number of properties handles.

CREATE VIEW BranchStats
AS 
   SELECT 
       branch.Bno Bno,
       Count (Distinct Staff.Bno) NumStaff,
       Count (Distinct property_for_rent.Sno) NumProps
   FROM 
       branch
   JOIN 
       Staff ON Staff.Bno = branch.Bno
   JOIN 
       property_for_rent ON property_for_rent.Sno = Staff.Sno
   GROUP BY 
       branch.Bno

Error

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'Distinct staff.Bno) NumStaff, Count (Distinct property_for_rent.Sno) Num' at line 4

Is there any wrong in my SQL statement? Need help

Answer 1

MySQL (by default) does not allow a space between the function name and the opening paren. So, try removing those spaces:

CREATE VIEW BranchStats AS 
   SELECT branch.Bno,
          Count(Distinct Staff.Bno) as NumStaff,
          Count(Distinct property_for_rent.Sno) as NumProps
   FROM branch JOIN 
        Staff
        ON Staff.Bno = branch.Bno JOIN 
        property_for_rent
        ON property_for_rent.Sno = Staff.Sno
   GROUP BY  branch.Bno;

This is explained in the documentation :

[ . . .] the parser uses the following rules by default to distinguish whether their names are being used as function calls or as identifiers in nonexpression context:

• To use the name as a function call in an expression, there must be no whitespace between the name and the following “(” parenthesis character.

• Conversely, to use the function name as an identifier, it must not be followed immediately by a parenthesis.

The requirement that function calls be written with no whitespace between the name and the parenthesis applies only to the built-in functions that have special considerations. COUNT is one such name.