The Dark Side of ALTER TABLE SQL Queries: SQL for Beginners

In this short mysql tutorial we'll walk you through one of the primary SQL queries allowing for database structure modification - the ALTER TABLE SQL query.

The speed of ALTER TABLE SQL queries is directly dependant on the structure of our database tables, the size of our tables, our web and database server, our database configuration, and the way we run SQL queries.

The core problem with SQL queries like ALTER TABLE is that it makes a copy of the table on the disk, then inserts data into it, performs all of the necessary operations, and only then swaps the old and new tables together. Keep that in mind the next time you run SQL queries on MySQL, Percona Server, MariaDB, or other database management system (in other database management systems the SQL query may as well work differently, so make sure to investigate.)

In its basic form ALTER TABLE queries look like so (a MySQL-based example):
ALTER TABLE [table_name] [action];
So if our table would be named "demo_table" and we'd want to add an index "demo_index" to a column "c1", we could run a query like so:
ALTER TABLE demo_table ADD INDEX demo_idx(c1);

Keep that in mind!

Below we provide you some sql interview questions and answers - those sql interview questions may be a necessity for your next developer interview, so always keep them in mind too. The questions are as follows:

Q: Are alter table sql queries the only way to modify data within a database?
A: No, multiple other sql queries can be employed as well.

Here are some of the most frequent sql interview questions and answers:
Q: ACID database vs base: what's the difference?
A: ACID stands for Atomicity Consistency Isolation and Durability, while BASE stands for Bascially Available, Soft State, Eventually Consistent DBMS.

Basically Available means that NoSQL database management systems ensure availability by replication.
Soft State means that there's no consistency - developers should enforce it themselves.
Eventually Consistent means that BASE databases don't enforce consistency, however, it can be achieved.

Q: What multi language database design approach should I take? Which DBMS does this technique work with?
A: We recommend you take the row-based approach to multi language database design. This technique works with MySQL, MariaDB, Percona Server, or any other DBMS.

Q: How to protect against SQL injection?
A: Don't pass user input into a SQL query. You really don't need to pass a mysql advanced tutorial to know this - it's that simple!

Q: What types of SQL indexes exist?
A: There are B-Tree indexes, R-Tree indexes, hash indexes, covering indexes, clustered indexes, multicolumn or composite SQL indexes, and prefix indexes.

Q: What is the most popular type of a mysql index?
A: A B-tree sql index is the most popular type of a mysql index.

Q: What is the file to adjust mysql server configuration?

Q: Is there a sql full course or any mysql tutorial that would cover mysql storage engines in more detail in all complex aspects?
A: Not that we know of, but if needed, we'll make a sql course talking about everything: sql basics, sql queries, sql vs nosql, sql for data analysis, etc.

Q: Is there a big data tutorial for those looking to work with big data on mysql server?

Q: I've heard that MyISAM performs row level locking?
A: No, that's a common misconception.

Q: MyISAM vs InnoDB performance - which one is better and why?
A: InnoDB - all of the features that were available in MyISAM are now available in InnoDB.

Enjoy!

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