What are the commands to modify data in sql

The commands to modify data in SQL mainly include the following categories: UPDATE command: update the specified field value in the row that meets the conditions. DELETE command: delete rows that meet the conditions. INSERT command: Inserts new rows into the table. MERGE command: Merge data into a table, supports updates and inserts. TRUNCATE command: Efficiently delete all rows in the table.

Commands to modify data in SQL

The commands used to modify data in SQL mainly include the following categories:

1. Update command

• UPDATE table name SET field name = new value WHERE condition;

This command is used to update the value of the specified field in the rows in the table that meet the specified conditions.

2. Delete command

• DELETE FROM table name WHERE condition;

This command uses Delete rows in the table that meet specified conditions.

3. Insert command

• INSERT INTO table name (field name 1, field name 2, ...) VALUES (value 1, Value 2, ...);

This command is used to insert a new row into the table and specify a value for the specified field.

4. Merge command

• MERGE INTO table name USING data source ON (connection condition) WHEN MATCHED THEN UPDATE SET ... WHEN NOT MATCHED THEN INSERT ...;

This command is used to merge data from a data source into a table. It supports both update and insert operations.

5. Truncate command

• TRUNCATE TABLE table name;

This command is used to delete All rows in the table, more efficient than the DELETE command.

Example:

Update the rows in the table that meet the conditions:

<code>UPDATE customers SET city = 'New York' WHERE state = 'NY';</code>

Delete the rows in the table that meet the conditions Rows:

<code>DELETE FROM orders WHERE order_date < '2023-01-01';</code>

Insert new rows into the table:

<code>INSERT INTO products (product_name, price) VALUES ('Apple', 10.00);</code>

Use the merge command to merge data:

<code>MERGE INTO customers
USING new_customers
ON (customer_id)
WHEN MATCHED THEN UPDATE SET first_name = new_customers.first_name
WHEN NOT MATCHED THEN INSERT (customer_id, first_name, last_name)
VALUES (new_customers.customer_id, new_customers.first_name, new_customers.last_name);</code>

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