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‎docs/sql/table-transformation/table-creation.md‎

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@@ -13,108 +13,42 @@ Welcome to the **Selecting Data** module! This foundational learning path is des
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### 📘 Creating SQL Table
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In this tutorial, you'll learn how to interpret and use rows in a database table. Tables are essential to storing structured data, and each **row** in a table represents a unique **item or record**.
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> Each row of a table represents a new item.
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In SQL, when creating a table, each column must have a data type that defines what kind of data it can hold. Common data types include:
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> `INTEGER` – whole numbers
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> `REAL` – decimal (floating-point) numbers
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> `TEXT` – strings of characters
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> Each column of a table represents a specific attribute of the data, such as `id`, `name`, or `username`.
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> These columns define the **type of information** stored for each item in the table.
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>Other types like `BLOB` and `NULL` exist but are not covered in this tutorial.
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For example, consider a table named `Friends`. Below is how a simple table might look:
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## Task: Sort a table using the `ORDER BY` clause
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## 🛠️ Example: Creating a Table
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### Lesson Overview
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After using `ORDER BY`, we specify the column by which we want to order the entries.
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For example, to sort by the `name` column:
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Let’s create a simple table named Directory, which holds the floor number and company name.
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>This CREATE TABLE statement defines a new table called Directory with two columns:
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The first step in ordering table is the SELECT
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ORDER BY helps you to arrange data in readable form
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Here FROM specify the table we are selecting from ountries.
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Here the query is ordering the number by name/.
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>`floor` — stores the floor number as an `INTEGER`
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>`company` — stores the company name as `TEXT`
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:::info
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<Tabs>
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<TabItem value="SQL Table" label="SQL Table">
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```sql title="Friends"
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| name | username|
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-----------|---------|
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Smith | 19 |
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Jones | 60 |
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Wilson | 25 |
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```
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</TabItem>
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<TabItem value="SQL Code" label="SQL Code">
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```sql title="Creating SQL Tables & db. "
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-- creating orders
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SELECT * FROM patients
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ORDER BY name;
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CREATE TABLE Directory (
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floor INTEGER,
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company TEXT
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);
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```
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</TabItem>
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<TabItem value="how-git-works" label="Output">
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| name | age |
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-------------------|--------------------------|
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Smith | 19 |
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Jones | 60 |
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Wilson | 25 |
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</TabItem>
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</Tabs>
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:::
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### Example Practice
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> To query data from a table, use the FROM clause followed by the table's name.
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For example, consider a table named `Friends`. Below is how a simple table might look:
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:::info
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<Tabs>
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<TabItem value="SQL Table" label="SQL Table">
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```sql title="Friends"
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| name | gdp |
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|---------|---------|
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| Greece | 187.46 |
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| Sweden | 474.15 |
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| Iceland | 21.6 |
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| Germany | 3449.05 |
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```
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</TabItem>
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<TabItem value="SQL Code" label="SQL Code">
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```sql title="Creating SQL Tables. "
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SELECT *
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FROM countries
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ORDER BY name;
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```
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</TabItem>
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<TabItem value="how-git-works" label="Output">
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| name | gdp |
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|---------|---------|
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| Germany | 3449.05 |
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| Greece | 187.46 |
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| Iceland | 21.6 |
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| Sweden | 474.15 |
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Query OK, table created successfully.
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</TabItem>
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</Tabs>
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:::tip
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When requesting data with SQL staments like SELECT, we say that we are making a query.
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From helps in select the name col from
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While not necessary but its a good practice to finish the sql queries with;
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✅ Tip: SQL keywords like CREATE TABLE, INTEGER, and TEXT are not case-sensitive, but using uppercase for SQL keywords improves readability.
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By following these best practices,
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:::
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### 🔄 Arranging ORDERS BY with ASC , DESC
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### 🧾 Inserting Data into a Table
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:::info
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Ordering text properties like name is different when comparing to the age
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We can order items in asseding starting with smalest value or deceding.
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Once a table structure is created using CREATE TABLE, the next step is to insert data into it. You can insert as many rows as you want, at any time.
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We’ll continue with the Directory table from earlier. Let’s insert a couple of company records.
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<Tabs>
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<TabItem value="SQL Table" label="SQL Table">
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```sql title="friends"
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| name | age |
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|--------|-----|
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| Smith | 19 |
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| Jones | 60 |
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| Wilson | 25 |
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```
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</TabItem>
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<TabItem value="SQL Code" label="SQL Code">
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```sql title="Creating SQL Tables. "
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SELECT *
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FROM patients
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ORDER BY age ASC;
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CREATE TABLE Directory (
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floor INTEGER,
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company TEXT
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);
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INSERT INTO Directory (floor, company)
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VALUES (1, 'Acme Inc.');
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INSERT INTO Directory (floor, company)
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VALUES (2, 'Homeflix');
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```
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</TabItem>
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<TabItem value="how-git-works" label="Output">
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| name | age |
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|--------|-----|
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| Smith | 19 |
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| Wilson | 25 |
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| Jones | 60 |
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| floor | company |
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|-------|-----------|
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| 1 | Acme Inc. |
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| 2 | Homeflix |
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</TabItem>
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</Tabs>
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:::
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## 🧹 Selecting with `DESC`
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For Text value it order by Alphabetically
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When arranging numerical value the item with smallest value in that coloumn comes first
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---
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:::info
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<Tabs>
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<TabItem value="SQL Table" label="SQL Table">
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```sql title="Subscribers"
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| name | age |
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|--------|-----|
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| Smith | 19 |
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| Jones | 60 |
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| Wilson | 25 |
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:::tip
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✅ Tip: Always match the order of columns in your INSERT INTO statement with the order of values inside VALUES().
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🚫 Avoiding Duplicate Table Creation
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When running a CREATE TABLE command, trying to create a table that already exists will usually result in an error. To avoid this, we can use the IF NOT EXISTS clause.
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```sql title="Creating SQL Tables.
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CREATE TABLE IF NOT EXISTS Directory (
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floor INTEGER,
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company TEXT
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);
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```
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</TabItem>
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<TabItem value="SQL Code" label="SQL Code">
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```sql title="Creating SQL Tables. "
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SELECT *
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FROM patients
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ORDER BY age DESC;
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```
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</TabItem>
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<TabItem value="how-git-works" label="Output">
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| name | age |
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|--------|-----|
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| Jones | 60 |
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| Wilson | 25 |
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| Smith | 19 |
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</TabItem>
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</Tabs>
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:::
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:::
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# ✅ What You Have Learned
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In this module, you learned the fundamentals of creating tables in SQL, including:
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- **Defining Table Structure**
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How to use the `CREATE TABLE` statement to define a new table and specify columns with appropriate data types.
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- **Common Data Types**
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The purpose of data types like `INTEGER` for numbers and `TEXT` for strings.
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# ✅ What You Have Learned
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- **Inserting Data**
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How to add rows to a table using the `INSERT INTO` statement.
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This module covers essential concepts related to ordering data in SQL:
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- **Preventing Duplicate Tables**
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Using `IF NOT EXISTS` with `CREATE TABLE` to avoid errors if the table already exists.
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- **ORDER BY Clause**
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Learn how to sort query results based on one or more columns using the `ORDER BY` keyword.
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- **Best Practices**
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Writing SQL keywords in uppercase for readability and matching column order in `INSERT INTO` statements.
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- **Ascending Order** (ASC)
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Understand that SQL sorts in ascending order by default, which is the same as explicitly using `ASC`.
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- **Descending Order** (DESC)
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Use the `DESC` keyword to sort results from highest to lowest or reverse alphabetical order.
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---
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- **Sort by Column Values**
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Practice sorting by numeric or text column values to organize data meaningfully.
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## 📝 Quiz: Test Your Knowledge
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#### 1. How can you ensure a table is only created if it doesn't already exist, to avoid errors?
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<details>
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<summary>Answer</summary>
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<ul>
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<li>By adding <code>IF NOT EXISTS</code> to the <code>CREATE TABLE</code> statement:</li>
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</ul>
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```sql
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CREATE TABLE IF NOT EXISTS Directory (
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floor INTEGER,
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company TEXT
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);
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```
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</details>
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#### 2. Complete the column definition for the `Tickets` table creation syntax with the appropriate column data types.
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```sql
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CREATE TABLE Tickets (
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qty _____,
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email _____
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);
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```
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<details>
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<summary>Answer</summary>
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<ul>
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<li>Specify <code>qty</code> as <code>INTEGER</code> and <code>email</code> as <code>TEXT</code>:</li>
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</ul>
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```sql
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CREATE TABLE Tickets (
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qty INTEGER,
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email TEXT
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);
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```
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</details>
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