Q71. Which statement updates data?
The **`UPDATE`** statement modifies existing data values in one or more rows of a table: ```sql UPDATE Customers SET email = 'new.email@example.com', updated_at = NOW() W...
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Q72. Keyword in UPDATE to change values?
The keyword used in an `UPDATE` statement to specify new values for columns is **`SET`**: ```sql UPDATE employees SET salary = salary * 1.10, title = 'Senior Software Eng...
Q73. Change "Jackson" to "Hawkins" in LastName?
To update all customers with the last name "Jackson" to "Hawkins": ```sql UPDATE Customers SET LastName = 'Hawkins' WHERE LastName = 'Jackson'; ``` ### Production Best Pr...
Q74. Which statement deletes data?
The **`DELETE`** statement removes existing rows from a table based on a condition: ```sql DELETE FROM Customers WHERE is_active = 0 AND last_login < '2023-01-01'; ``` ##...
Q75. Delete records where FirstName is "John"?
To delete all rows where `FirstName` equals "John": ```sql DELETE FROM Customers WHERE FirstName = 'John'; ``` *Safety Warning:* If you accidentally omit `WHERE FirstName...
Q76. What is FROM used for?
The **`FROM`** clause defines the source table(s), views, joined datasets, or subqueries from which rows are read: ```sql SELECT u.username, p.title FROM users u INNER JO...
Q77. DELETE vs TRUNCATE?
See the comparison table above. Key differences: `DELETE` is DML (row-by-row, rollbackable, fires triggers, has WHERE). `TRUNCATE` is DDL (bulk page deallocation, faster,...
Q78. Which statement creates a table?
The **`CREATE TABLE`** statement defines and provisions a new table schema: ```sql CREATE TABLE Customers ( customer_id INT AUTO_INCREMENT PRIMARY KEY, first_name VARCHAR...
Q79. What is database collation and how does it affect SQL queries?
Collation defines the **rules for comparing and sorting** characters. It works with the character set. - `utf8mb4_general_ci`: Case-insensitive, faster - `utf8mb4_unicode...
Q80. What is AUTO_INCREMENT?
Automatically generates sequential unique integers for a column, typically the PRIMARY KEY. ```sql CREATE TABLE users (id INT AUTO_INCREMENT PRIMARY KEY, name VARCHAR(50)...