如何在mysql中具有外键属性的表中插入新记录

Question

What is wrong in this statement since customers table has only one record

INSERT INTO CART (Cartid,custid,Pid)
VALUES ('2',SELECT(custid from CUSTOMERS), SELECT (Pid from Products where Pname ='shirts'))

Answer 1

The correct syntax is:

INSERT INTO CART (Cartid, custid, Pid)
    VALUES (2,
            (SELECT custid FROM CUSTOMERS LIMIT 1),
            (SELECT Pid FROM Products WHERE Pname = 'shirts' LIMIT 1)
           );

Your parentheses are in the wrong place.

Notes:

• I added the LIMIT just to enforce that one row is returned.
• I removed the single quotes around '2' , because ids are usually number.
• You probably should not be inserting the id; it should be an auto-increment column.

Answer 2

Make sure that the cart table id is primary key and auto_increment. Get the customer id and store in a variable. You can try something similar like this

INSERT INTO CART (Cartid,custid,Pid) VALUES ('', SELECT custid from CUSTOMERS  WHERE custid = '$customer_id'),(SELECT Pid FROM Products WHERE Pname = 'shirts' LIMIT 1));