Two step process to convert NULL to NOT NULL. We will assume that we have a column with a data type of VARCHAR and we are trying to convert it to allow NOT NULL Values. Step 1: Convert all values to NOT NULL UPDATE TableName SET ColumnName = ” WHERE ColumnName IS NULL Step 2: …
What is a Join in SQL? Inner join returns rows when there is at least one match in both tables while Left Join returns rows from the right and matched rows from the left table. Left join When to use Left Join Instead of Inner Join in SQL To choose which side of the table …
SQL DISTINCT clause is used to remove duplicate records. SELECT DISTINCT returns distinct(different) values. DISTINCT can be used with aggregate functions: COUNT, AVG, MAX, MIN. Syntax: SQL SELECT DISTINCT based on one column You can SELECT DISTINCT values from one column in a table. Below is the syntax. SQL SELECT DISTINCT based on multiple columns …
The SELECT statement in SQL is used to retrieve data from a database. Mostly used to retrieve all data in a table and data from desired table columns (fields). SELECT Syntax In the above syntax, you are selecting data from exact columns or fields indicated as column1, column2, column3 and so on. To select all …
SQL stands for Structured Query Language. SQL is used to store, query, modify, manipulate and retrieve data stored in a relational database. Usually pronounced as “ess-que-ell”. According to ANSI (American National Standards Institute), it is the language for relational database management systems. All relational database systems (RDBMS) accept the use of SQL (MS Access, MySQL, …
SQL has become a powerful tool for data analysis and manipulation of data. The EOMONTH() function returns the last day of the month of a specified date. EOMONTH() can be used as a worksheet function (WS) in Excel. However, to get the last day of previous month in SQL can be achieved with the following SQL …
What is Performance tuning Performance tuning in SQL is the practice of ensuring SQL queries run as fast as possible. SQL Performance tuning can be difficult, especially when working with large amount of data. SQL performance tuning is handled by Database Administrators (DBA’s) in large corporations. However, to improve the speed of data retrieval with …
The understanding of data trends, patterns, attributes and its relationship to human behavior and business is a result of data-driven cycle in analytics. Data Science revolves around data. We associate quarterly and annual growth of businesses based on data received which are facts to help make business decisions. Most improved business methodologies are data-driven. So, …
SQL (Structured Query Language) is a vital skill for a career in analytics, Big Data, databases and Data Science. As a go-to tool for pulling and manipulating data in a database, we have listed and explained top 50 interview questions in SQL from basic to advanced questions. These interview questions will equip you for any …
What is Data Data is a collection of words, images, sound, letters and observations for analysis, reference and research purpose. What is Redundancy in Data Data redundancy is the duplication of data in a table or database. When data is duplicated we consume more memory space in storage devices . Back-up storage devices can be …