Difference between ALTER and UPDATE Command in SQL
1. ALTER Command :
ALTER SQL command is a DDL (Data Definition Language) statement. ALTER is used to update the structure of the table in the database (like add, delete, modify the attributes of the tables in the database).
// add a column to the existing table ALTER TABLE tableName ADD columnName columnDefinition; // drop a column from the existing table ALTER TABLE tableName DROP COLUMN columnName; // rename a column in the existing table ALTER TABLE tableName RENAME COLUMN olderName TO newName; // modify the datatype of an already existing column in the table ALTER TABLE table_name ALTER COLUMN column_name column_type;
2. UPDATE Command :
UPDATE SQL command is a DML (Data manipulation Language) statement. It is used to manipulate the data of any existing column. But can’t be change the table’s definition.
// table name that has to update UPDATE tableName // which columns have to update SET column1 = value1, column2 = value2, ...,columnN=valueN. // which row you have to update WHERE condition
Note : Without WHERE clause, all records in the table will be updated.
Difference Between ALTER and UPDATE Command in SQL :
SR.NO ALTER Command UPDATE Command 1 ALTER command is Data Definition Language (DDL). UPDATE Command is a Data Manipulation Language (DML). 2 Alter command will perform the action on structure level and not on the data level. Update command will perform on the data level. 3 ALTER Command is used to add, delete, modify the attributes of the relations (tables) in the database. UPDATE Command is used to update existing records in a database. 4 ALTER Command by default initializes values of all the tuple as NULL. UPDATE Command sets specified values in the command to the tuples. 5 This command make changes with table structure. This command makes changes with data inside the table. 6 Example : Table structure, Table Name, SP, functions etc. Example : Change data in the table in rows or in column etc.
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