Essential SQL commands for Data Science
Published: 2023-03-11 12:05:36

Lets talk about one of the most commonly used language by data scientists. This is a must know language as it is used to extract data from databases, and for any career in data, then you will be sure to use it. we will not get into details about it for now, but we will talk about the essential commands that one will likely have to deal with everytime.
lets dive in.
Structured Query Language (SQL) is a standard language for managing and manipulating data stored in relational databases. Data science is all about gathering, analyzing, and extracting meaningful insights from data. Therefore, it is essential for data scientists to have a good understanding of SQL commands to effectively work with data. In this article, we will discuss some of the essential SQL commands for data science.

SELECT
SELECT is one of the most basic and essential SQL commands. It is used to extract data from one or more tables based on specific conditions. The basic syntax of the SELECT statement is as follows:
SELECT column_name(s)
FROM table_name
WHERE condition;

The SELECT statement retrieves data from the specified columns in the table, and the WHERE clause specifies the conditions for filtering the data.

JOIN
JOIN is another important SQL command that is used to combine data from two or more tables based on a common column. There are several types of JOIN operations, including INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN. The syntax for an INNER JOIN is as follows:
SELECT column_name(s)
FROM table1
INNER JOIN table2
ON table1.column_name = table2.column_name;

In an INNER JOIN, only the records that have matching values in both tables are returned.

GROUP BY
GROUP BY is a SQL command that is used to group data based on one or more columns. It is often used in conjunction with aggregate functions such as COUNT, SUM, AVG, and MAX. The syntax for a GROUP BY statement is as follows:
SELECT column_name(s), aggregate_function(column_name)
FROM table_name
WHERE condition
GROUP BY column_name(s);

The GROUP BY statement groups the data based on the specified column(s), and the aggregate function is applied to each group.

ORDER BY
ORDER BY is used to sort the data in a table based on one or more columns. It can be used in conjunction with the ASC and DESC keywords to specify the sorting order. The syntax for an ORDER BY statement is as follows:
SELECT column_name(s)
FROM table_name
WHERE condition
ORDER BY column_name(s) ASC|DESC;

The ORDER BY statement sorts the data in ascending or descending order based on the specified column(s).

HAVING
HAVING is similar to the WHERE clause, but it is used to filter data based on aggregate functions. It is often used in conjunction with the GROUP BY statement. The syntax for a HAVING statement is as follows:
SELECT column_name(s), aggregate_function(column_name)
FROM table_name
WHERE condition
GROUP BY column_name(s)
HAVING condition;

The HAVING statement filters the data based on the aggregate function(s) applied to the grouped data.

In conclusion, SQL is an essential tool for data scientists, and understanding its commands is crucial for effective data analysis. The SELECT, JOIN, GROUP BY, ORDER BY, and HAVING commands are some of the essential SQL commands for data science. By mastering these commands, data scientists can efficiently manipulate and analyze data stored in relational databases.