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SQL ÖÐÐ޸ıí½á¹¹µÄÓï¾ä

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1. Ìí¼ÓÁÐ

ALTER TABLE table_name ADD column_name data_type

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ALTER TABLE employees ADD salary INT

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2. ÐÞ¸ÄÁÐ

ALTER TABLE table_name ALTER COLUMN column_name data_type

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ALTER TABLE employees ALTER COLUMN salary DECIMAL(10,2)

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3. ɾ³ýÁÐ

ALTER TABLE table_name DROP COLUMN column_name

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ALTER TABLE employees DROP COLUMN bonus

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4. ¸ü¸ÄÁÐÃû³Æ

ALTER TABLE table_name RENAME COLUMN old_column_name TO new_column_name

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ALTER TABLE employees RENAME COLUMN first_name TO name

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5. Ìí¼ÓÔ¼Êø

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ALTER TABLE table_name ADD PRIMARY KEY (column_name)

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ALTER TABLE employees ADD PRIMARY KEY (employee_id)

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ALTER TABLE table_name ADD FOREIGN KEY (column_name) REFERENCES referenced_table(column_name)

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ALTER TABLE orders ADD FOREIGN KEY (customer_id) REFERENCES customers(customer_id)

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ALTER TABLE table_name ADD UNIQUE (column_name)

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ALTER TABLE employees ADD UNIQUE (email)

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6. ɾ³ýÔ¼Êø

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ALTER TABLE table_name DROP PRIMARY KEY

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ALTER TABLE table_name DROP FOREIGN KEY column_name

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ALTER TABLE table_name DROP INDEX index_name (ÆäÖÐ index_name ÊÇΨһԼÊøµÄÃû³Æ)

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