How to Add Data to MySQL Database — SQL Technical Interview Questions & Answers

How to Add Data to MySQL Database

How to Add Data to MySQL Database

  • INSERT INTO students (roll, name, marks) VALUES (12, 'Asha', 72); adds one row. List the columns. Don’t rely on column order in the table — tomorrow someone ALTERs it.
  • Many rows: INSERT INTO students (roll, name, marks) VALUES (12,'Asha',72), (13,'Kabir',40); One statement, two rows.
  • AUTO_INCREMENT: skip that column, MySQL fills it. Duplicate PRIMARY KEY → error 1062. INSERT IGNORE skips the bad row. ON DUPLICATE KEY UPDATE changes the old row instead.
  • Trap: INSERT INTO students VALUES ('Asha', 12, 72) with columns in the wrong order. Trap: inserting NULL into NOT NULL.
  • On the example next to this theory: How to Add Data to MySQL Database: create two demo rows, then SELECT qty >= 2 ordered. Say which labels come back.

Technical Interview Tip: INSERT INTO students (roll, name, marks) VALUES (12, 'Asha', 72);

Code Examples for How to Add Data to MySQL Database

How to Add Data to MySQL Database — sample query

-- How to Add Data to MySQL Database
CREATE TABLE demo (
  id INTEGER PRIMARY KEY,
  label TEXT NOT NULL,
  qty INTEGER DEFAULT 0
);
INSERT INTO demo (id, label, qty) VALUES
  (1, 'alpha', 2),
  (2, 'beta', 5);
SELECT label, qty FROM demo WHERE qty >= 2 ORDER BY qty DESC;

How to Add Data to MySQL Database: create two demo rows, then SELECT qty >= 2 ordered. Say which labels come back.

How to Explain How to Add Data to MySQL Database to an Interviewer

Write an INSERT.

INSERT INTO students (roll, name, marks) VALUES (12, 'Asha', 72);

How do you insert two rows?

Two tuples in VALUES (12,'Asha',72), (13,'Kabir',40)