Question

I’m trying to select mltiple rows from tow table :
first table is donor

       CREATE TABLE donor(
   donor_number INT NOT NULL AUTO_INCREMENT,
   d_name VARCHAR(30) NOT NULL,
   mobile_number INT NOT NULL,
   blood_group VARCHAR(20) NULL,
      dob DATE NOT NULL,
   gender ENUM('male','female') NOT NULL,
    govid INT(10) NOT NULL,
   PRIMARY KEY (donor_number  )

);

second table is blood_donation

    CREATE TABLE blood_donation(

   donor_number INT NOT NULL,
   date_of_donate DATE NOT NULL,
   blood_group VARCHAR(20) NULL,
   serial_number INT(10) NOT NULL,
   blood_component ENUM('wb','prcb') NOT NULL,
   PRIMARY KEY (donor_number , date_of_donate ),
   FOREIGN KEY (donor_number) REFERENCES donor(donor_number) 

   );

with this select statement:

        SELECT 
serial_number,
blood_group
FROM blood_donation
WHERE date_of_donate = '2012-07-18'
UNION ALL
SELECT 
blood_group
FROM donor
WHERE donor.donor_number=blood_donation.donor_number;

but, I get error

    SQL state 42S22: Unknown column 'blood_donation.donor_number' in 'where clause'
any idea????

Answer 1

Actually you should not be using UNION but JOIN 🙂

you query will look like this

SELECT 
  blood_donation.serial_number,
  donor.blood_group 
FROM
  blood_donation ,
  donor 
WHERE donor.donor_number = blood_donation.donor_number  AND date_of_donate = '2012-07-18' ;