Database creation and selection in MySQL - Step-by-Step Execution

Concept Flow - Database creation and selection

Start

↓

Write CREATE DATABASE statement

↓

Execute CREATE DATABASE

↓

Database created?

No→Error: Fix and retry

Yes↓

Write USE statement

↓

Execute USE statement

↓

Database selected

↓

Ready for further commands

First, create a new database with CREATE DATABASE. Then select it with USE to work inside it.

Execution Sample

MySQL

CREATE DATABASE school;
USE school;

This code creates a database named 'school' and then selects it for use.

Execution Table

Step	SQL Command	Action	Result	Notes
1	CREATE DATABASE school;	Create database named 'school'	Success	Database 'school' created
2	USE school;	Select database 'school' for use	Success	Current database set to 'school'
3		Ready for next commands	N/A	Database 'school' is active

💡 Database 'school' created and selected successfully, ready for further commands.

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
Current Database	None	None	school	school

Key Moments - 2 Insights

Why do we need to run USE after CREATE DATABASE?

CREATE DATABASE only makes the database but does not select it. USE sets the current database to run commands inside it, as shown in execution_table step 2.

What happens if we try to create a database that already exists?

The CREATE DATABASE command will fail with an error. You must fix the name or drop the existing database first. This is implied in the flow where creation success is checked.

Visual Quiz - 3 Questions

Look at the execution table, what is the current database after step 1?

A mysql

B school

C None

D test

💡 Hint

Check the 'Current Database' variable in variable_tracker after step 1.

At which step does the database become selected for use?

A Step 2

B Step 1

C Step 3

D Before Step 1

💡 Hint

Look at the 'Action' and 'Result' columns in execution_table for step 2.

If the CREATE DATABASE command fails, what should you do next?

A Run USE command anyway

B Fix the error and retry CREATE DATABASE

C Drop the database and then run USE

D Nothing, the database is created automatically

💡 Hint

Refer to the concept_flow where failure leads to 'Error: Fix and retry'.

Concept Snapshot

CREATE DATABASE db_name;  -- creates a new database
USE db_name;              -- selects the database to work in
CREATE DATABASE only makes the database,
USE sets it as current for commands.
Always run USE after creating to select.

Full Transcript

To create and select a database in MySQL, first run CREATE DATABASE with your chosen name. This command makes the database but does not select it. Next, run USE with the database name to select it for your session. After USE, all commands run inside that database. If CREATE DATABASE fails, fix the error before continuing. This process ensures you have a database ready and selected for your work.

Practice

1. What does the CREATE DATABASE command do in MySQL?

easy

A. It selects a database to use.

B. It deletes an existing database.

C. It creates a new database to store data.

D. It shows all databases available.

Solution

1. Step 1: Understand the purpose of CREATE DATABASE

   This command is used to make a new database where you can store tables and data.

2. Step 2: Differentiate from other commands

   Deleting databases uses DROP DATABASE, selecting uses USE, and showing uses SHOW DATABASES.

3. Final Answer:

   It creates a new database to store data. -> Option C

4. Quick Check:

   CREATE DATABASE = create new database [OK]

Hint: Remember: CREATE makes new, USE picks existing [OK]

Common Mistakes:

• Confusing CREATE with USE command
• Thinking CREATE deletes databases
• Mixing CREATE with SHOW DATABASES

2. Which of the following is the correct syntax to select a database named shop in MySQL?

easy

A. SELECT DATABASE shop;

B. CHOOSE DATABASE shop;

C. OPEN DATABASE shop;

D. USE shop;

Solution

1. Step 1: Recall the command to select a database

   In MySQL, the command to start using a database is USE database_name;.

2. Step 2: Check each option's syntax

   Only USE shop; is valid syntax. Others are incorrect commands.

3. Final Answer:

   USE shop; -> Option D

4. Quick Check:

   USE selects database [OK]

Hint: Use USE to pick your database [OK]

Common Mistakes:

• Using SELECT instead of USE
• Trying OPEN or CHOOSE commands (not valid)
• Missing semicolon at end

3. What will be the result of the following commands?

CREATE DATABASE testdb;
USE testdb;
SHOW TABLES;

medium

A. Lists all tables in the database 'testdb'.

B. Shows an error because 'testdb' does not exist.

C. Creates a table named 'testdb'.

D. Shows all databases available.

Solution

1. Step 1: Create and select the database

   The command CREATE DATABASE testdb; makes a new database named 'testdb'. Then USE testdb; selects it for use.

2. Step 2: Show tables in the selected database

   SHOW TABLES; lists all tables in the current database. Since 'testdb' is empty, it will show an empty list but no error.

3. Final Answer:

   Lists all tables in the database 'testdb'. -> Option A

4. Quick Check:

   SHOW TABLES lists tables in current DB [OK]

Hint: SHOW TABLES lists tables in current database [OK]

Common Mistakes:

• Thinking SHOW TABLES shows databases
• Assuming error because database is new
• Confusing CREATE DATABASE with CREATE TABLE

4. Identify the error in the following MySQL commands:

CREATE DATABASE mydb
USE mydb;

medium

A. Database name 'mydb' is invalid.

B. Missing semicolon after CREATE DATABASE statement.

C. USE command cannot follow CREATE DATABASE.

D. CREATE DATABASE should be lowercase.

Solution

1. Step 1: Check syntax of each command

   MySQL commands must end with a semicolon. The first line misses a semicolon after CREATE DATABASE mydb.

2. Step 2: Verify other parts

   The database name 'mydb' is valid, USE can follow CREATE DATABASE, and case does not matter for commands.

3. Final Answer:

   Missing semicolon after CREATE DATABASE statement. -> Option B

4. Quick Check:

   Semicolon ends commands [OK]

Hint: Always end SQL commands with semicolon [OK]

Common Mistakes:

• Forgetting semicolon at end of statements
• Thinking database names must be uppercase
• Believing USE cannot follow CREATE DATABASE

5. You want to create two databases named sales and inventory, then select sales to work with. Which sequence of commands is correct?

hard

A. CREATE DATABASE sales; CREATE DATABASE inventory; USE sales;

B. USE sales; CREATE DATABASE sales; CREATE DATABASE inventory;

C. CREATE DATABASE sales, inventory; USE sales;

D. CREATE DATABASE sales; USE inventory; CREATE DATABASE inventory;

Solution

1. Step 1: Create both databases separately

   Each database must be created with its own CREATE DATABASE command ending with a semicolon.

2. Step 2: Select the 'sales' database to use

   After creating, use USE sales; to select the 'sales' database for work.

3. Final Answer:

   CREATE DATABASE sales; CREATE DATABASE inventory; USE sales; -> Option A

4. Quick Check:

   Create each DB then USE the one you want [OK]

Hint: Create each DB separately, then USE the desired one [OK]

Common Mistakes:

• Trying to create multiple databases in one command
• Using USE before creating the database
• Selecting wrong database after creation