SQL
Queries and joins, indexes, transactions, normalisation and query performance.
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- 1What is a database?Junior
- 2What is SQL? What is SQL used for?Junior
- 3What is a relational database?Junior
- 4How does a relational database differ from a non-relational one?Junior
- 5What is a table in a database?Junior
- 6What is a database schema?Junior
- 8What is a field?Junior
- 9What is an SQL query?Junior
- 10What are DDL, DML, DCL, TCL?Junior
- 11What data types exist in SQL?Junior
- 12What is a primary key (PRIMARY KEY)?Junior
- 13What is a foreign key (FOREIGN KEY)?Junior
- 15Tell me about normal forms (1NF, 2NF, 3NF)Junior
- 16What is data integrity?Junior
- 17What is data redundancy?Junior
- 1How do you create a table in SQL?Junior
- 2How do you drop a table?Junior
- 3How do you add a new column to a table?Junior
- 5How do you drop a column from a table?Junior
- 6How does DROP TABLE differ from DELETE?Junior
- 7What is DML in SQL?Junior
- 8How do you insert a record into a table?Junior
- 9How do you update a record in a table?Junior
- 10How do you delete a record in a table?Junior
- 11What does the TRUNCATE command do?Junior
- 12How do you insert several rows in one query?Junior
- 13What happens if you don't specify all required fields in INSERT?Junior
- 14What is auto-increment (AUTO_INCREMENT / SERIAL)?Junior
- 15How do you make a field unique in a row?Junior
- 17How do you delete all rows from a table?Junior
- 18What does ON DELETE CASCADE do?Junior
- 19What does the MERGE command do?Junior
- 20What does the SELECT command do in SQL?Junior
- 21How do you select all columns of a table?Junior
- 22How do you select only specific columns?Junior
- 23How do you select unique rows from a table?Junior
- 24What does DISTINCT do?Junior
- 25What does GROUP BY do?Junior
- 26What does LIMIT do in SQL?Junior
- 27How do you return only the first 10 records?Junior
- 29Where can subqueries be used?Junior
- 30How do you filter rows by condition?Junior
- 31What does the WHERE operator do?Junior
- 32What does LIKE do?Junior
- 33What does the BETWEEN operator do?Junior
- 34How do you set several filter conditions at once?Junior
- 35What does the IN operator do?Junior
- 36What does NOT IN do?Junior
- 37How do you work with logical operator precedence?Junior
- 39What does ORDER BY do?Junior
- 40How do you sort data in ascending order?Junior
- 41How do you sort data in descending order?Junior
- 42What do ASC and DESC do?Junior
- 43How do you sort by multiple fields?Junior
- 44What do NULLS FIRST and NULLS LAST do?Junior
- 45How do you combine ORDER BY and LIMIT?Junior
- 2Why do you need to combine tables?Junior
- 3How does JOIN differ from a subquery?Junior
- 4Can you join more than two tables?Junior
- 5What are relationships between tables?Junior
- 6Tell me about a 1:1 (one-to-one) relationshipJunior
- 7Tell me about a 1:many (one-to-many) relationshipJunior
- 8Tell me about a many:many relationshipJunior
- 10What does LEFT JOIN do?Junior
- 11What does RIGHT JOIN do?Junior
- 12What does FULL OUTER JOIN do?Junior
- 13What does CROSS JOIN do?Middle
- 14What is a cartesian product?Middle
- 15What does USING do in a JOIN?Middle
- 1What is data aggregation in SQL?Junior
- 2What does the COUNT() aggregate function do?Junior
- 3What does SUM() do?Junior
- 5What do MIN() and MAX() do?Junior
- 6What does GROUP BY do?Junior
- 7How does grouping work in SQL?Junior
- 8How are aggregate functions related to GROUP BY?Junior
- 9How do you group data by a single field?Junior
- 10How do you group data by multiple fields?Junior
- 11What does HAVING do? How does HAVING differ from WHERE?Junior
- 1What is an index in SQL? Why do we need indexes?Junior
- 2How does an index speed up data lookup?Junior
- 4How does an index affect insert and update speed?Junior
- 5What does the term "index tree" mean?Middle
- 6What is a clustered index (clustered index)?Junior
- 7What is a non-clustered index (non-clustered index)?Junior
- 8What is a covering index (covering index)?Middle
- 9What is a composite index?Middle
- 10Why aren't indexes always useful?Middle
- 11How are indexes implemented inside a DBMS?Middle
- 12What is a B-Tree index?Middle
- 14When are Hash indexes more effective?Middle
- 15How do you create an index in SQL?Junior
- 16What is a "functional index"?Middle
- 1What is a transaction in SQL?Junior
- 2Why do we need transactions?Junior
- 3What does the term "atomicity" mean?Junior
- 4Why are transactions important for data integrity?Junior
- 5What is ACID?Middle
- 7What does "Consistency" mean in ACID?Middle
- 8What does "Isolation" mean in ACID?Middle
- 9What does "Durability" mean in ACID?Middle
- 10What happens if a transaction fails midway?Junior
- 11How do you start a transaction in SQL?Junior
- 12What does the COMMIT command do?Junior
- 13What does the ROLLBACK command do?Junior
- 14Why do transactions guarantee atomicity?Middle
- 15How do transactions ensure data consistency?Middle
- 16What is a transaction isolation level?Middle
- 17What is a lock in SQL?Middle
- 1What is a view (VIEW) in SQL?Junior
- 2Why do we need views?Junior
- 3How do you create a view?Junior
- 4Can you insert data into a view?Junior
- 5Can you update data through a view?Junior
- 6Can you delete data through a view?Junior
- 7How do views affect performance?Middle
- 8What is a function in SQL?Junior
- 9How do you create a function?Junior
- 11What is a deterministic function?Middle
- 12What is a non-deterministic function?Middle
- 13What is a trigger in SQL?Middle
- 14Why do we need triggers?Junior
- 15What types of triggers exist?Middle
- 16What does a row-level trigger do?Middle
- 18What are the pros and cons of using triggers?Middle
- 1What does database administration include?Junior
- 2What does the term "instance" mean for a database?Junior
- 3What is a "schema" in SQL?Junior
- 4How do clients connect to a database server?Junior
- 5What are "configuration files" in a DBMS?Junior
- 6Why do we need an undo / rollback log?Middle
- 7What is a user in SQL?Junior
- 8How do you create a user?Junior
- 9What are access privileges (privileges)?Junior
- 11What types of backups exist?Junior
- 12How often should you back up?Junior
- 13Why do we need database monitoring?Junior
- 14What metrics matter when administering a database?Junior
- 15What does "SQL injection" mean?Junior
- 16How do you protect against SQL injections?Junior
- 1What is database scaling?Middle
- 2How does scaling differ from optimization?Junior
- 3What is a "bottleneck" in a database?Junior
- 4What types of scaling exist?Junior
- 6What is horizontal scaling (horizontal scaling)?Middle
- 7Why is it important to separate read and write load?Middle
- 8What is PgBouncer and why do you need it?Middle
- 9What is replication in SQL?Junior
- 10How does replication help scale a database?Middle
- 11What does "master-replica" architecture mean?Middle
- 12How does synchronous replication differ from asynchronous replication?Middle
- 13What is partitioning (partitioning)?Middle
- 15What is sharding (sharding)?Middle
- 16How does partitioning differ from sharding?Middle
- 17What sharding strategies exist?Middle
- 18What is load balancing (load balancing)?Middle
- 19How do you distribute requests across multiple replicas?Middle
- 20How does scaling affect data consistency?Middle
- 21What is a database cluster?Middle