DBA / Database

What is the difference between synchronous and asynchronous replication modes in AlwaysOn?

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What is a transaction and what are transaction isolation levels in PostgreSQL?

Difference between a procedure and a function.

How do you understand that these specific indexes on these columns will help achieve performant queries? How do you determine high selectivity?

Что такое Transaction ID Wraparound в PostgreSQL?

How was the PostgreSQL cluster organized? Replication scheme and fault tolerance?

Что такое WAL (Write-Ahead Log)?

How to implement partial transaction rollback (not full, but up to a certain point)?.

What are indexes in a database?

Tell us about the Always On High Availability technology in MS SQL Server.

What is BULK COLLECT and FORALL, and why do they work faster?

What is msdb in SQL Server?

What is a package of procedures? What does it consist of?

What is the difference between EXPLAIN and EXPLAIN ANALYZE?

What is a CTE (Common Table Expression)? What are the advantages? Is the CTE materialized?

What is the difference between checkpointer and background writer?

What types of replication exist in PostgreSQL? What is the difference between physical and logical replication?

Are multiple DML operations executed in a single transaction in the procedure?

What can be done if an index is not used due to a function on a column?

Tell me about types of indexes. What are they and which ones have you used most often?