SQL SELECT FIRST Row

SQL SELECT FIRST Row

The SQL SELECT FIRST statement is used to retrieve the first row from a query result. This command is essential for fetching the top record based on specific sorting criteria, often used to get the earliest or highest value in a column. Note that different SQL databases may use different syntax for this operation (e.g., LIMIT 1 in MySQL).

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Syntax

-- For SQL Server
SELECT TOP 1 column1, column2, ...
FROM table_name
ORDER BY column_name;

-- For MySQL and PostgreSQL
SELECT column1, column2, ...
FROM table_name
ORDER BY column_name
LIMIT 1;

-- For Oracle
SELECT column1, column2, ...
FROM table_name
ORDER BY column_name
FETCH FIRST 1 ROW ONLY;

• SELECT TOP 1: This is the SQL keyword used in SQL Server to specify the top 1 row.
• column1, column2, ...: These specify the names of the columns to retrieve.
• FROM: This is the SQL keyword used to specify the table.
• table_name: This specifies the name of the table from which to retrieve the row.
• ORDER BY column_name: This specifies the column by which to sort the rows to determine the first one.
• LIMIT 1: This specifies the limit of one row to be returned (MySQL and PostgreSQL).
• FETCH FIRST 1 ROW ONLY: This specifies the limit of one row to be returned (Oracle).

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Example

Let's go through a complete example that includes creating a database, creating a table, inserting data into the table, and then using the SELECT FIRST statement to retrieve the first row.

Step 1: Creating a Database

This step involves creating a new database named example_db.

CREATE DATABASE example_db;

In this example, we create a database named example_db.

Step 2: Creating a Table

In this step, we create a table named employees within the previously created database.

USE example_db;

CREATE TABLE employees (
    id INT AUTO_INCREMENT PRIMARY KEY,
    first_name VARCHAR(50) NOT NULL,
    last_name VARCHAR(50) NOT NULL,
    email VARCHAR(100),
    hire_date DATE
);

Here, we define the employees table with columns for id, first_name, last_name, email, and hire_date. The id column is set as the primary key and will auto-increment.

Step 3: Inserting Data into the Table

This step involves inserting some sample data into the employees table.

INSERT INTO employees (first_name, last_name, email, hire_date) VALUES ('John', 'Doe', 'john.doe@example.com', '2023-01-01');
INSERT INTO employees (first_name, last_name, email, hire_date) VALUES ('Jane', 'Smith', 'jane.smith@example.com', '2023-02-01');
INSERT INTO employees (first_name, last_name, email, hire_date) VALUES ('Alice', 'Johnson', 'alice.johnson@example.com', '2023-03-01');
INSERT INTO employees (first_name, last_name, email, hire_date) VALUES ('Bob', 'Brown', 'bob.brown@example.com', '2023-04-01');

Here, we insert four rows of data into the employees table.

Step 4: Using the SELECT FIRST Statement

This step involves retrieving the first row from the employees table using the SELECT FIRST statement (syntax for SQL Server).

SELECT TOP 1 * FROM employees
ORDER BY hire_date;

This command will return the first row from the employees table ordered by the hire_date column.

For MySQL and PostgreSQL, the equivalent command is:

SELECT * FROM employees
ORDER BY hire_date
LIMIT 1;

For Oracle, the equivalent command is:

SELECT * FROM employees
ORDER BY hire_date
FETCH FIRST 1 ROW ONLY;

These commands will return the first row from the employees table ordered by the hire_date column in their respective SQL database systems.