Invalid Column Name in SQL Server Management Studio - sql

Question

When I execute this query in SQL Server Management Studio, this error appears:
'Msg 207, Level 16, State 1, Line 1
Invalid column name 'ACCOUNT_NO'.'
This is the code for the query:
DECLARE #largeaccnumber INT = ACCOUNT_NO
DECLARE #smallaccnumber INT
SET #smallaccnumber = (SELECT LEFT(#largeaccnumber, 6))
SELECT DNADRX.CODE,
DNADDR.NAME,
DNADDR.TYPE,
DNADDR.MAIL_NAME,
ADDRESS_LINE1,
ADDRESS_LINE2,
ADDRESS_LINE3,
TOWN_CITY,
COUNTY_STATE,
COUNTY_STATE_CODE,
COUNTRY,
POST_ZIP,
LAST_STAT_DATE,
ACCOUNT_NO
FROM DNADRX,
DNADDR,
BACCNT
WHERE DNADDR.CODE = DNADRX.ADDRESS_CODE
AND DNADDR.CODE = #smallaccnumber
ORDER BY DNADRX.CODE
I want the query to display the data from the columns of the different tables (the columns are listed in the SELECT bit of the query) from 3 different tables (DNADRX, DNADDR, BACCNT), and the factor linking all 3 tables together is the 6 digit code (ACCOUNT_NO in the BACCNT table, ADDRESS_CODE in the DNADRX table and CODE in the DNADDR table). Originally, ACCOUNT_NO from table BACCNT was 8 digits long, but I reduced it to the first 6 digits using SELECT LEFT and assigned this 6 digit value to the variable #smallaccnumber.
Whenever I try to execute the query, it keeps telling me that 'ACCOUNT_NO' is an invalid code name. I have checked the spelling, refreshed using IntelliSense and tried 'BACCNT.ACCOUNT_NO' instead of just 'ACCOUNT_NO' on the first line of the query but it still won't work (instead it says that the multi-part identifier could not be bound when I try 'BACCNT.ACCOUNT_NO').
I am really new to SQL coding so sorry if the answer to my problem is really simple.
Thank you for your assistance :)

Answer 1

You can try something like this.
This assumes you know the 6 character code. This query will only find results IF there is a record matching in EVERY table. If one table doesn't find a matching record this query will return NOTHING. If you want to find a row even if a recrod is missing from a table, replace the "INNER JOIN" with "LEFT OUTER JOIN"
SELECT Dnadrx.Code,
Dnaddr.Name,
Dnaddr.Type,
Dnaddr.Mail_Name,
Address_Line1,
Address_Line2,
Address_Line3,
Town_City,
County_State,
County_State_Code,
Country,
Post_Zip,
Last_Stat_Date,
Account_No
FROM Dnaddr
INNER JOIN BACCNT ON DNAADDR.CODE = BACCNT.ACCOUNT_NO
INNER JOIN Dnadrx ON Dnaaddr.Code=Dnaadrx.Address_Code
WHERE Dnaddr.Code='YOUR 6 CHARACTER CODE GOES HERE'
ORDER BY Dnadrx.Code;