anchor.diff:      ;
   
   alterTable
  -    : ALTER TABLE existClause_ onlyClause_ tableName asteriskClause_ alterDefinitionClause_
  +    : ALTER TABLE tableExistClause_ onlyClause_ tableName asteriskClause_ alterDefinitionClause_
       ;
   
   alterIndex
  -    : ALTER INDEX existClause_ indexName alterIndexDefinitionClause_
  +    : ALTER INDEX indexExistClause_ indexName alterIndexDefinitionClause_
       ;
   
   dropTable
  -    : DROP TABLE existClause_ tableNames
  +    : DROP TABLE tableExistClause_ tableNames
       ;
   
   dropIndex
  -    : DROP INDEX (CONCURRENTLY)? existClause_ indexName (COMMA_ indexName)*
  +    : DROP INDEX concurrentlyClause_ indexExistClause_ indexNames
       ;
       
   truncateTable
  -    : TRUNCATE TABLE? ONLY? tableNameParts
  +    : TRUNCATE TABLE? onlyClause_ tableNamesClause
       ;
   
   createTableSpecification_
  
positive.code:     | addConstraintSpecification
      | ALTER CONSTRAINT ignoredIdentifier_ constraintOptionalParam
      | VALIDATE CONSTRAINT ignoredIdentifier_
      | DROP CONSTRAINT existClause_ ignoredIdentifier_ (RESTRICT | CASCADE)?
      | (DISABLE | ENABLE) TRIGGER (ignoredIdentifier_ | ALL | USER)?
      | ENABLE (REPLICA | ALWAYS) TRIGGER ignoredIdentifier_
      | (DISABLE | ENABLE) RULE ignoredIdentifier_
  
negative.code:     ;
  
  dropColumnSpecification
      : DROP COLUMN? columnExistClause_ columnName (RESTRICT | CASCADE)?
      ;
  
  columnExistClause_
      : (IF EXISTS)?
      ;
      
  modifyColumnSpecification
      : alterColumn (SET DATA)? TYPE dataType collateClause? (USING simpleExpr)?
      | alterColumn SET DEFAULT expr
  