SQL basics including joining 2 or more tables

1. SQL
Querying Multiple Tables

2. Now It’s Relational!
SELECT c.CD_NAME, p.PREF_NAME, c.IN_STOCK
FROM CD_INVENTORY c, PERFORMERS p
WHERE c.PREF_ID = p.PREF_ID
AND c.IN_STOCK < 15;

3. More than 2 Tables!
SELECT c.CD_NAME, p.PREF_NAME, t.TYPE_NAME
FROM CD_INVENTORY c, PERFORMERS p,
PREF_TYPE t
WHERE c.PREF_ID = p.PREF_ID
AND p.TYPE_ID = t.TYPE_ID
AND TYPE_NAME = ‘Popular’;

4. Another Way to Join
SELECT c.CD_NAME, p.PREF_NAME, c.IN_STOCK
FROM CD_INVENTORY JOIN PERFORMERS p ON
c.PREF_ID = p.PREF_ID
WHERE c.IN_STOCK < 15;

5. LEFT OUTER JOIN
● Used to return all the rows from the LEFT
table, even if they don’t match
SELECT i.TITLE, t.TYPE_NAME, i.STOCK
FROM CD_INFO i LEFT OUTER JOIN CD_TYPE i
ON i.TYPE_ID = t.TYPE_ID;

6. RIGHT OUTER JOIN
Used to return all the rows from the RIGHT
table, even if they don’t match
SELECT i.TITLE, t.TYPE_NAME, i.STOCK
FROM CD_INFO i RIGHT OUTER JOIN CD_TYPE i
ON i.TYPE_ID = t.TYPE_ID;

7. FULL OUTER JOIN
Used to return all the UNMATCHED rows from
both tables
SELECT i.TITLE, t.TYPE_NAME, i.STOCK
FROM CD_INFO i FULL OUTER JOIN CD_TYPE i
ON i.TYPE_ID = t.TYPE_ID;

8. Combine Query Results
SELECT *
FROM CDS_CONTINUED
UNION
SELECT *
FROM CDS_DISCONTINUED;
● Must have same columns and data types!