11 advanced MySQL questions

 

Explain MySQL architecture
. - The front layer
takes care of network connections and security authentications, the
middle layer does the SQL query parsing, and then the query is handled
off to the storage engine. A storage engine could be either a default
one supplied with MySQL (MyISAM) or a commercial one supplied by a
third-party vendor (ScaleDB, InnoDB, etc.)
Explain MySQL locks
. - Table-level locks allow the
user to lock the entire table, page-level locks allow locking of
certain portions of the tables (those portions are referred to as
tables), row-level locks are the most granular and allow locking of
specific rows.
Explain multi-version concurrency control in MySQL
.
- Each row has two additional columns associated with it - creation
time and deletion time, but instead of storing timestamps, MySQL stores
version numbers.
What are MySQL transactions?
- A set of instructions/queries that should be executed or rolled back as a single atomic unit.
What’s ACID?
- Automicity - transactions are
atomic and should be treated as one in case of rollback. Consistency -
the database should be in consistent state between multiple states in
transaction. Isolation - no other queries can access the data modified
by a running transaction. Durability - system crashes should not lose
the data.
Which storage engines support transactions in MySQL?
- Berkeley DB and InnoDB.
How do you convert to a different table type?
- ALTER TABLE customers TYPE = InnoDB
How do you index just the first four bytes of the column?
- ALTER TABLE customers ADD INDEX (business_name(4))
What’s the difference between PRIMARY KEY and UNIQUE in MyISAM?
- PRIMARY KEY cannot be null, so essentially PRIMARY KEY is equivalent to UNIQUE NOT NULL.
How do you prevent MySQL from caching a query?
- SELECT SQL_NO_CACHE …
What’s the difference between query_cache_type 1 and 2?
- The second one is on-demand and can b