The ALTER command is a DDL command that allows you to change the structure of existing database tables by adding, changing, renaming, or removing columns and constraints. Using the ALTER command, you can create columns, rename columns, delete columns, and modify the data type of columns.
To add, delete, or edit columns in an existing table, use the ALTER TABLE statement. The ALTER TABLE statement can also be used to add and remove constraints from a table.
TABLE table name ALTER TABLE ALTER COLUMN column name TYPE data type; Changes the datatype of a column in the table. TABLE table name ALTER TABLE RENAME TO new table name; Changes the name of a table in the database to which you're currently connected.
A Transact-SQL query can be used to change a table's definition or data. Use the Data Editor, as explained in Connected Database Development, to graphically see or enter data in a table.
A DDL (Data Definition Language) statement is ALTER. UPDATE, on the other hand, is a DML (Data Manipulation Language) command. ALTER is used to change the table's structure (add/remove fields, indexes, and so forth). UPDATE, on the other hand, is used to update data.
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