Join in sql

Question

hi
i have 2 tables
table A
ID     p_id     loc
1        3122       oh
2        3423        VA
tableB
p_id   p_type 
3122     s
3122      e
i need to join by p_id, but when i am join i am getting 2 rows,i juse need one row whichever comes first
current outout
1          3122              s
1          3122               e
i just need any of 1 row ,s or e whichever comes first, any idea

Answer 1

Hi,
When you join the two tables, you always join on unique keys. In this case you do not have unique values, therefore when you join you will get more outcomes of the same p_id.
If you want to make join, make sure your ID is unique.
With the following example there is a join on the ID column, I have used that column as a unique key. This way you will have from every ID number one line as output.
CREATE TABLE #A
ID INT,
P_ID INT,
LOC VARCHAR(20)
INSERT INTO #A(ID,P_ID,LOC)
VALUES
(1,3122,'OH'),
(2,3423,'VA');
--TRUNCATE TABLE #A
CREATE TABLE #B
ID INT,
P_ID INT,
P_TYPE VARCHAR(20)
INSERT INTO #B(ID,P_ID,P_TYPE)
VALUES
(1,3122,'S'),
(2,3122,'E');
--TRUNCATE TABLE #B
--SELECT * FROM #A
SELECT *
FROM #A
INNER JOIN #B ON #A.ID=#B.ID
This is the output of the above SELECT statement.
Regards,
Reshma
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