Notes

SQL Statements

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INSERT Statement:

  • Adds new records to a table.
  • To selectively insert into a specific columns
  • Insert multiple records
INSERT INTO logins VALUES (1, 'admin', 'p@ssw0rd', '2020-07-02');
INSERT INTO logins(username, password) VALUES ('john', 'john123!');
INSERT INTO logins(username, password) VALUES ('tom', 'tom123!'), ('jane', 'jane123!');

SELECT Statement

  • Retrieves data from a table.
  • To select specific columns
SELECT * FROM logins;
SELECT username, password FROM logins;

DROP Statement

  • Deletes entire tables or databases permanently.
DROP TABLE logins;

ALTER Statement

  • Modifies a table’s structure.
  • Rename a column:
  • Modify a column’s data type:
  • Drop a column:
ALTER TABLE logins ADD newColumn INT;
ALTER TABLE logins RENAME COLUMN newColumn TO newerColumn;
ALTER TABLE logins MODIFY newerColumn DATE;
ALTER TABLE logins DROP newerColumn;

UPDATE Statement

  • Updates specific records in a table.
UPDATE logins SET password='change_password' WHERE id > 1;

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