sub-queries
COALESCE NULL-values NULLIF NVL General-Functions NV2
collation binary-collation character-sets case-insensitive-collation
INSERT-statement
join inner-join
sub-queries correlated-subquery synchronized-subquery
ROWNUM Oracle
statements language-elements clauses queries predicates expressions insignificant-whitespaces
FROM-clause optimization
Oracle DROP-statement MySQL MS-Access DROP-INDEX DB2 SQL-server