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Welcome! Are you ready to learn SQL? SQL (Structured Query Language) is a standard language for managing data held in a relational database management system. Whether you aim to be a data analyst or a backend developer, knowledge of SQL is fundamental in today’s digital world. This blog post is crafted for SQL beginners, and we’ll guide you with a practical approach to understand the rudiments of this powerful language.
What is SQL?
SQL is used to communicate with a database. Developed in the 70s, SQL is very popular due to its simplicity and efficiency. SQL operations include inserting, querying, updating, deleting rows of data, and modifying database structures.
Basic SQL Commands
There are five basic commands in SQL: SELECT, INSERT, UPDATE, DELETE, and ALTER. Let’s explain how each of these commands work with code examples.
1. SELECT
The SELECT statement is used to select data from a database. The data returned is stored in a result table, called the result-set.
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SELECT column1, column2, ... FROM table_name; |
2. INSERT
The INSERT INTO statement is used to insert new rows of data into a table.
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INSERT INTO table_name (column1, column2, column3, ...) VALUES (value1, value2, value3, ...); |
3. UPDATE
The UPDATE statement is used to modify the existing records in a table.
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UPDATE table_name SET column1 = value1, column2 = value2, ... WHERE condition; |
4. DELETE
The DELETE statement is used to delete existing records in a table.
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DELETE FROM table_name WHERE condition; |
5. ALTER
The ALTER TABLE statement is used to add, delete/drop or modify columns in the existing table. It is also used to add and drop various constraints on the existing table.
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ALTER TABLE table_name ADD column_name datatype; |
Hopefully, with these basic SQL commands, you now have a springboard from which to plunge into the deeper waters of SQL. Always remember, practice is key. Begin by trying out these commands, and see how they reflect on the database. In time, you’ll navigate through these commands with much ease. Happy learning!