复制alter_specification: ADD [COLUMN] create_definition [FIRST | AFTER column_name ] or ADD INDEX [index_name] (index_col_name,改表...) or ADD PRIMARY KEY (index_col_name,...) or ADD UNIQUE [index_name] (index_col_name,...) or ALTER [COLUMN] col_name {SET DEFAULT literal | DROP DEFAULT} or CHANGE [COLUMN] old_col_name create_definition or MODIFY [COLUMN] create_definition or DROP [COLUMN] col_name or DROP PRIMARY KEY or DROP INDEX index_name or RENAME [AS] new_tbl_name or table_options 1.2.3.4.5.6.7.8.9.10.11.12.13.