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Tag Archives: SQL-basics

SQL stands for Structured Query Language. Which is based on relational algebra and schema is fixed in this which means data is stored in the… Read More
MySQL is an easy-to-use RDBMS. Many organizations prefer to use it because of its easy maintainability, easier to prepare schemas, stored procedures, triggers, and database… Read More
In oracle there are different type of user accounts system, sys, hr and many more. This user accounts is by default created by oracle .If… Read More
JSON stands for Javascript Object Notation. It is mainly used in storing and transporting data. Mostly all NoSQL databases like MongoDB, CouchDB, etc., use JSON… Read More
To retrieve data from the single table we use SELECT and PROJECTION operations but to retrieve data from multiple tables we use JOINS in SQL.… Read More
Prerequisite – SQL Injection While checking for SQL injection we all discover various error messages. Let us figure out the basic cause behind each error… Read More
1. ALTER Command: ALTER SQL command is a DDL (Data Definition Language) statement. ALTER is used to update the structure of the table in the… Read More
1. Procedures: A procedure is a combination of SQL statements written to perform specified tasks. It helps in code re-usability and saves time and lines… Read More
The lateral keyword represents a lateral join between two or more tables. It joins the output of the outer query with the output of the… Read More
Prerequisite – DDL, DQL, DML, DCL, and TCL Commands DDL is Data Definition Language that is used to define data structures. For example: create table,… Read More
Prerequisite: SQL | GROUP BY Error: Column ‘col’ is invalid in the select list because it is not contained in either an aggregate function or… Read More
Prerequisite – SQL Trigger | Student Database For example, given Library Book Management database schema with Student database schema. In these databases, if any student… Read More
Trigger: A trigger is a stored procedure in database which automatically invokes whenever a special event in the database occurs. For example, a trigger can… Read More
The Common Table Expressions (CTE) were introduced into standard SQL in order to simplify various classes of SQL Queries for which a derived table was… Read More
DISTINCT is useful in certain circumstances, but it has drawback that it can increase load on the query engine to perform the sort (since it… Read More

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