SQL Join Cheatsheet

a.rb

(-----A-----(-----)     B     )
SELECT           <columns>
FROM             table_A  A
LEFT JOIN        table_B  B
ON               A.key = B.key

(-----A-----(     )     B     )
SELECT           <columns>
FROM             table_A  A
LEFT JOIN        table_B  B
ON               A.key = B.key
WHERE            B.key IS NULL

(     A     (-----)     B     )
SELECT           <columns>
FROM             table_A  A
INNER JOIN       table_B  B
ON               A.key = B.key

(-----A-----(-----)-----B-----)
SELECT           <columns>
FROM             table_A  A
FULL OUTER JOIN  table_B  B
ON               A.key = B.key

(-----A-----(     )-----B-----)
SELECT           <columns>
FROM             table_A  A
FULL OUTER JOIN  table_B  B
ON               A.key = B.key
WHERE            A.key IS NULL
OR               B.key IS NULL

(     A     (-----)-----B-----)
SELECT           <columns>
FROM             table_A  A
RIGHT JOIN       table_B  B
ON               A.key = B.key

(     A     (     )-----B-----)
SELECT           <columns>
FROM             table_A  A
RIGHT JOIN       table_B  B
ON               A.key = B.key
WHERE            A.key IS NULL