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Whether you want to delve into the world of data management or merely learn a new handy skill, Structured Query Language (SQL) is an essential tool in today’s digital society. With its ability to handle data efficiently, SQL is the leading programming language heavily used by database administrators, developers, and data analysts. Essentially, SQL lets you access, manipulate, and interact with data in relational databases. Let’s dive into it!
What is SQL?
SQL, an acronym for Structured Query Language, is a standardized programming language used in managing and manipulating relational databases. It can perform operations such as insert, update, delete and retrieve data from a database.
SQL Terminology
Before we explore the specific SQL queries, let’s familiarize ourselves with a few key SQL terms:
- Database: A structured set of data.
- Table: A structured list of data of a specific type in a database.
- Row: A record in a table.
- Column: An attribute or field of a data set.
- Primary Key: A unique identifier of a record in a table.
Basic SQL Queries
By far the easiest and most straightforward way to understand SQL is to see it in action. Below we’ll delve into the basic queries: SELECT, INSERT UPDATE and DELETE.
1. SELECT Command
The SELECT statement is one of the most commonly used commands. It allows you to select and display data from a database. Here is its basic syntax:
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SELECT column1, column2, ... FROM table_name; |
For instance, if we need to select all rows from the ‘Students’ table:
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SELECT * FROM Students; |
2. INSERT INTO Command
The INSERT INTO statement is used to insert a new row into a table:
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INSERT INTO table_name (column1, column2, column3, ...) VALUES (value1, value2, value3, ...); |
For example, to insert a new student into the ‘Students’ table, you might use:
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INSERT INTO Students (FirstName, LastName, Age) VALUES ('John', 'Doe', 22); |
3. UPDATE Command
This command is used to modify existing records in a table. We use it like this:
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UPDATE table_name SET column1 = value1, column2 = value2, ... WHERE condition; |
For example, to update the age of student John Doe, we would use:
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UPDATE Students SET Age = 23 WHERE FirstName = 'John' AND LastName = 'Doe'; |
4. DELETE Command
The DELETE statement is used to delete existing records from a table:
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DELETE FROM table_name WHERE condition; |
For instance, you could delete our record concerning John Doe like this:
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DELETE FROM Students WHERE FirstName = 'John' AND LastName = 'Doe'; |
Conclusion
This was a basic introduction to SQL and its primary commands. There is far more to explore as your need for data manipulation, and management grows. However, with these often-used commands, you have a good starting point for understanding how SQL interacts with data. Happy querying!