MySQL update modify data table structure SQL statement

Use of the Alter command in MySQL to edit the table structure.

Modify Table Name

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ALTER TABLE test rename test1;

Modify a field type

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ALTER TABLE employee change depno depno Int (5) is not null;

Add index

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ALTER TABLE name add index index name (field name 1[, field Name 2 ...]); Example: ALTER TABLE employee ADD index emp_name (name);

Index of the Primary keyword

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ALTER TABLE name Add primary key (field name); Example: ALTER TABLE employee ADD primary key (ID);

Index with unique restriction criteria

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ALTER TABLE name add unique index name (field name); Example: ALTER TABLE employee add unique emp_name2 (cardnumber);

View the index of a table

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Show the index from table name; Example: Show index from employee;

Delete an index

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ALTER TABLE name DROP INDEX index name; Example: ALTER TABLE employee DROP INDEX emp_name;

To add a table field:

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ALTER TABLE table_name ADD field_name Field_type; View table: SELECT * FROM table_name;

To modify the original field name and type:

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ALTER TABLE table_name Change old_field_name new_field_name field_type;

To delete a field:

1: Delete Column

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ALTER TABLE Table name drop Column name ALTER TABLE table_name drop field_name