SQL INNER JOIN
Learn SQL INNER JOIN step by step: matching rows, table aliases, joining three tables, JOIN with WHERE and GROUP BY, USING, and duplicate-row pitfalls.
SQA Tools Blog
Learn testing and automation, one article at a time
Free tutorials, solved practice problems and interview prep for QA and automation engineers: Python, Playwright, Selenium, SQL, Git and more.
1,677Articles
1,141Solved Python problems
7Topics
100%Free
Latest articles
1,677 articles · page 59 of 140SQL AUTO_INCREMENT
Generate ids automatically with MySQL AUTO_INCREMENT: define it, read LAST_INSERT_ID, set the start value, why gaps appear, and IDENTITY equivalents.
SQL CHECK Constraint
Learn the SQL CHECK constraint in MySQL 8: validate ranges, lists and multi-column rules, named checks, the NULL rule, and adding or dropping a CHECK.
SQL NOT NULL Constraint
Learn the SQL NOT NULL constraint: require values in a column, what errors look like, adding NOT NULL to an existing column safely, and NOT NULL with DEFAULT.
SQL UNIQUE Constraint
Learn the SQL UNIQUE constraint in MySQL: unique columns, composite unique keys, NULL behaviour, adding and dropping UNIQUE, and UNIQUE vs PRIMARY KEY.
SQL FOREIGN KEY
Learn SQL FOREIGN KEY constraints in MySQL: referential integrity, parent and child tables, errors 1451 and 1452, ON DELETE CASCADE, SET NULL and RESTRICT.
SQL PRIMARY KEY
Learn the SQL PRIMARY KEY: what makes a good key, single-column and composite keys, natural vs surrogate keys, errors, and adding a primary key in MySQL.
Python SQLite
Learn Python's sqlite3 module: connect to a database, create tables, insert with parameters, query and fetch rows, update, delete, transactions and pandas.
Python JSON Module Tutorial
Elevate your data interchange skills with the Python json module and unlock the ability to create flexible, interoperable data solutions.
Python Datetime
Learn the Python datetime module: create dates and times, format with strftime, parse with strptime, date arithmetic with timedelta, and time zones.
Python sys Module
Learn the Python sys module: read command-line arguments with sys.argv, exit with a status code, check sys.path and versions, and use stdin and stderr.
Python Collections Module
Learn Python's collections module: Counter for counting, defaultdict for grouping, deque for queues, namedtuple, OrderedDict and ChainMap, with examples.
Preparing for a QA interview?
Take free timed mock tests with answers and explanations.