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SELECT Statement in SQL

Overview

The SELECT statement in SQL is utilized to recover information from a database. It is the foremost commonly utilized SQL command. The SELECT statement can be utilized to choose columns from a table, such as a particular set of columns or all of the columns from a table.

The SQL SELECT Statement

A medical clinic was looking to streamline their patient records and needed to quickly access information about their patients' medical histories. The clinic chose to contribute in a SQL database to keep track of patient data. To do this, the clinic utilized the SELECT statement to form a query that permitted them to rapidly distinguish, analyze, and sort the patient information. Lets jump into it further.

The SELECT statement is utilized to choose information from a database. The result is put away in a result table, called the result-set.

Syntax:


SELECT column1, column2, ...
FROM table_name;

Example:

Table: customers

TitleColumn 1
first_namelast_name
JohnSmith
JaneDoe
JoeBloggs

SELECT first_name, last_name
FROM customers;

This code will select the first and last name of every customer in the customers table. The result will be a table with two columns, one for the first names of the customers and one for the last names.

SELECT Column

In SQL, the term "column" alludes to a single field inside a database table. A column can contain a range of data types such as text, numbers, or dates, and it can be utilized to store a single value or multiple values. To choose a particular column inside a table, the SQL SELECT statement is utilized, followed by the title of the column.

Syntax

SELECT [Column1, Column2, ...]
FROM [Table]
WHERE [Conditions];

Example:

NameSalary
John Smith$45,000
Jane Doe$50,000
Bob Johnson$55,000
SELECT name
FROM employees;

This code employs an SQL SELECT statement to recover information from a table called "employees". It indicates that only the "name" column ought to be returned from the table, meaning that all other columns will be prohibited from the resulting information set.

SELECT

The SELECT statement is used to retrieve data from a database. The syntax for the SELECT statement is:

SELECT column1, column2, ...
FROM table_name
WHERE condition;

The SELECT statement allows you to select specific columns from a table in the database. You can specify multiple columns using a comma-separated list. The WHERE clause is used to filter the results, so that only rows matching the specified condition are returned.

Example:

first_namelast_namesalary
JohnSmith55000
JaneDoe60000
AdamJohnson80000
SELECT first_name, last_name, salary
FROM Employees
WHERE salary > 50000;

This code is a SQL statement that selects the first name, last name, and salary from the Employees table. It will return all the rows from the table that match the condition specified in the WHERE clause, which is that the salary is greater than $50,000.

Best Practices to follow while using SELECT statement

  1. Limit the number of columns: Only select the columns that are needed for the query. This reduces the amount of data that needs to be retrieved from the database, resulting in faster query execution times.
  2. Use table aliases: Table aliases make the query easier to read and write. They also reduce the amount of typing required when referencing columns in the query.
  3. Use indexes: Create indexes on columns that are frequently used in WHERE and JOIN clauses. This improves query performance by reducing the amount of data that needs to be scanned to find the required data.

Conclusion

Utilizing the SELECT statement, the clinic was able to rapidly recognize, analyze, and sort the patient information. This permitted the clinic to rapidly and precisely distinguish which patients had gone to the clinic as of late, what medicines they had gotten, and any potential wellbeing dangers that will get to be addressed. With this data, the clinic was able to supply way better care and make strides in their quiet involvement.

Key takeaways

  1. SELECT is utilized to recover records from one or more tables in a database.
  2. The syntax for a SELECT statement is SELECT [columns] FROM [table].
  3. SELECT can be combined with other SQL clauses, such as WHERE and Order BY, to make more complex queries.
  4. To choose all columns from a table, utilize SELECT * FROM [table].
  5. To choose particular columns from a table, utilize SELECT [columns] FROM [table].
  6. To constrain the columns returned by a query, utilize the WHERE clause.
  7. To sort the comes about returned by a query, utilize the Order BY clause.
  8. To combine information from numerous tables, utilize the Connect clause.
  9. To aggregate data, use the GROUP BY clause.
  10. To use calculations in a query, use the HAVING clause.

Quiz

1. What is the SQL command to select all columns from a table? 

  1. SELECT * 
  2. SELECT ALL 
  3. SELECT COLUMNS 
  4. SELECT ALL COLUMNS

Answer: a. SELECT *

2. What is the SQL command to select records from a table? 

  1. SELECT RECORDS 
  2. SELECT DATA 
  3. SELECT ALL
  4. SELECT ROWS

Answer: d. SELECT ROWS

3. What is the SQL command to select specific columns from a table? 

  1. SELECT SPECIFIC 
  2. SELECT COLUMNS 
  3. SELECT ALL 
  4. SELECT SPECIFIC COLUMNS

Answer: d.SELECT SPECIFIC COLUMNS

4. What is the SQL command to select records from a table that meet certain criteria? 

  1. SELECT CONDITIONS 
  2. SELECT WHERE 
  3. SELECT MATCH 
  4. SELECT CRITERIA

Answer: b. SELECT WHERE

Module 4: DML CommandsSELECT Statement in SQL

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