Databases

In Structured Query Language (SQL), a “view” is a virtual table whose contents are the result of a specific query to one or more tables. This guide provides an overview of what SQL views are and why they can be useful. It also highlights how you can create, query, modify, and destroy views using standard SQL syntax.

Many database designs separate information into different tables based on how certain data points relate to one another. Even in cases like this, it’s likely that there will be times when someone will want to retrieve information from more than one table at a time. A common way of accessing data from multiple tables in a single SQL operation is to combine the tables with a JOIN clause. This guide outlines how to retrieve data from multiple tables by joining them together.

Like many computer languages, SQL allows the use of various wildcard characters. Wildcards are special placeholder characters that can represent one or more other characters or values. This is a convenient feature in SQL, as it allows you to search your database for your data without knowing the exact values held within it. This tutorial will go over how to query data using SQL’s designated wildcards.

In certain Structured Query Language (SQL) statements, WHERE clauses can be used to limit what rows the given operation will affect. SQL allows users to retrieve granular result sets by providing a variety of different types of predicates, each of which use a specific operator to evaluate rows. This guide will outline two types of predicates: range predicates which use the BETWEEN operator, and set membership predicates which use the IN operator.

In Structured Query Language (SQL) statements, WHERE clauses limit what rows the given operation will affect. This guide will go over the general syntax used in WHERE clauses. It will also outline how to combine multiple search condition predicates in a single WHERE clause to filter data with more granularity, as well as how to use the NOT operator to exclude, rather than include, rows that meet a given search condition.

One of the most fundamental parts of working with databases is the practice of retrieving information about the data held within them. In relational database management systems, any operation used to retrieve information from a table is referred to as a query. In this guide, we will discuss the basic syntax of queries in Structured Query Language (SQL) as well as some of their more commonly used functions and operators.

As the name implies, DELETE operations irreversibly delete one or more rows of data from a database table. Being such a fundamental aspect of data management, it’s important for SQL users to understand how the DELETE statement behaves and how it deletes data. This guide will go over how to use SQL’s DELETE syntax to delete data from one or more tables. It will also explain how foreign key constraints handle DELETE operations.

When working with a database, there may be times when you need to change data that’s already been inserted into it; you may need to correct a misspelled entry, or perhaps you have information to add to an incomplete record. SQL provides the UPDATE statement which allows users to change existing data in a table. This guide outlines how you can use SQL’s UPDATE syntax to change data in one or more tables. It will also explain how SQL handles UPDATE operations that conflict with foreign keys.