Databases
A database is a named container that holds related tables. A single MySQL server can host many databases at once for example, one for a blog, one for a school system, one for an online store completely separate from each other. Grouping tables into a database keeps related data together and unrelated data apart. A students database might hold students, grades, and attendance tables; it has no reason to also contain a store's products table. You can see what databases exist on a server with SHOW DATABASES;, and switch into one to work with it using USE database_name;. Once you've run USE, your following commands (like SELECT or CREATE TABLE) apply inside that database by default. Think of a MySQL server as a filing cabinet, each database as one labeled drawer, and each table inside it as one folder of related records.
Why this matters
- ·Separate databases keep unrelated projects from ever mixing or colliding.
- ·One server can safely host many databases for many different apps at once.
- ·SHOW DATABASES and USE make it quick to see and switch between projects.
Common mistakes
- ·Running a command without first USE-ing the right database can affect the wrong project.
- ·Deleting a database (DROP DATABASE) removes every table and every row inside it there is no undo.
- ·Giving databases vague names makes it easy to lose track of which one holds what.
+--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | school | +--------------------+ 4 rows in set
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Frequently asked questions
Yes. A single MySQL server commonly hosts many separate databases for many separate projects.
Practice questions
Question 1
Write the command that lists every database on the server.
PHP runs on a server, not in the browser this shows the expected output instead of a live one.
Question 2
Write the command that switches your session into a database called library.
PHP runs on a server, not in the browser this shows the expected output instead of a live one.
Quick check
Just for this topic answer honestly, then check yourself.
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