SELECT 
   sum (Tabl1.field1), 
   table1.field2, 
   table2.field1 
FROM table1 
GROUP BY table1.field2 
LEFT JOIN table2 
ON table1.field2=table2.field2

SELECT * | { [ DISTINCT | ALL] < value expression >.,..}
   FROM { < table name > [ < alias > ] }.,..
   [ WHERE <predicate>]
   [ GROUP BY { <column name> | <integer> }.,..]
   [ HAVING <predicate>]
   [ ORDERBY { <column name> | <integer> }.,..]

   [ { UNION [ALL]

SELECT * | { [DISTINCT | ALL] < value expression >.,..}
   FROM { <table name> [<alias>]} .,..
   [ WHERE < predicate >
   [ GROUP BY { <columnname> | <integer> }.,..]
   [ HAVING <predicate >]
   [ ORDER BY { <columnname> | <integer> }.,..] } ] ...;