In SQL, performing division operation sometimes leads to errors when divided by zero . This error is " divide by zero " which can disrupt your query execution . To avoid this situation, we can use the following methods: Use NULL IF function Use CASE statement Use SET ARITHABORT OFF Use WHERE Now we will discuss these methods one by one with the help of examples. Use NULLIF function In this method , if both the arguments are ... Read More

Selecting Multiple Columns Based On Condition Structured Query Language is used to manage and query databases. One common use case of databases is to select single columns or multiple columns of a table based on specific conditions. The SQL SELECT statement is used to retrieve data from a database. These conditions help filter the data to match your query. These conditions are : AND and OR IN BETWEEN Syntax Following is the syntax for selecting multiple columns is − SELECT col 1 , col ... Read More

A foreign key is a field (or collection of fields) in one table that refers to the primary key in another table. The table containing the foreign key is called the child table, and the table containing the primary key is called the parent table. A foreign key ensures that the value in the foreign key column must match a value in the primary key column of the referenced table, maintaining referential integrity between the two tables. Characteristics of a Foreign Key A foreign key creates a relationship between two tables. ... Read More

In a SQL Server database, slow-running queries can severely impact performance, leading to delays, timeouts, and increased server load. Identifying and optimizing these queries is crucial to ensuring a smooth and efficient database operation. Common reasons for slow queries include missing indexes, inefficient joins, high I/O operations, outdated statistics, and parameter sniffing issues. Prerequisites Before identifying slow queries, ensure you have the necessary access and tools: Database Administrator (DBA) Privileges − You need appropriate permissions to run diagnostic queries. SQL Server Management Studio (SSMS) − This tool provides execution plans ... Read More

When working with large datasets in SQL, you may often need to retrieve only the first row of each group based on a specific column. For example, you might want to fetch the earliest order for each customer, the highest-paid employee in each department, or the latest transaction per user. Selecting the First Row of Each Group In data analysis and database management, grouping data and extracting specific rows—such as the first or earliest record in each group—is a common and essential task. This technique is beneficial for scenarios like: Finding the first transaction ... Read More

In SQL, joining tables is an essential operation that combines data from multiple sources. While joining two tables is straightforward many real-world scenarios require joining three or more tables to retrieve comprehensive information. This article explains how to join three or more tables, complete with examples. Understanding Joins SQL joins are used to combine rows from two or more tables based on a related column. The Common types of joins include: INNER JOIN: Returns records that have matching values in both tables. ... Read More

Sometimes, you need to get data from SQL Server that falls between two specific dates or times, like finding all orders placed within a week or all activities that happened during a certain time frame. Writing the right query can be challenging if you're not familiar with how to filter data by date and time. In this article, we will show you how to easily select data between two dates and times in SQL Server using simple queries. Steps to Write Queries for Selecting Data Between Dates and Times As we're going to write queries to filter data ... Read More

To query data in SQL where you need to match multiple values within the same column, you can use operators like IN and OR. For example, how would you find employees in the "Sales" or "Marketing" departments, or list those with job titles like "Manager" or "Salesperson"? These are common scenarios when filtering data based on multiple conditions in SQL: The IN operator allows you to match values from a list, while OR helps combine multiple conditions efficiently. In this article, we'll show you how to write SQL queries to match multiple values within the same column, making it easier ... Read More

SQL (Structured Query Language) is a programming language used to manage and interact with databases. In this case, the goal is to find the highest salary in each department from a table that contains employee data, including their salaries and the departments they work in. We'll write an SQL query to find the highest salary for each department, which is useful for analyzing salary trends, setting pay standards, and making informed business decisions. Finding the Highest Salary of Each Department To find the highest salary in each department, use SQL's GROUP BY and MAX() functions. The GROUP BY ... Read More

Filtering data by date or datetime is a common requirement when working with SQL queries. Whether you're retrieving records for a specific date, a range of dates or precise timestamps SQL provides robust tools to handle such scenarios. Understanding Date and DateTime Data Types The SQL databases support various data types for storing the date and time information: DATE: Stores only the date (e.g. 2025-01-07). DATETIME: The Stores both date and time (e.g. 2025-01-07 14:30:00). TIMESTAMP: The Stores date and time with time zone information in some ... Read More