Category: Advanced SQL

SQL Transactions A transaction is a unit or sequence of work that is performed on a database. Transactions are accomplished in a logical order, whether in a manual fashion by a user or automatically by some sort of a database program. A transaction is the propagation of one or more changes to the database. For…

SQL uses the term NULL to represent a non-existent data value in the database. These values are not the same as an empty string or a zero. They don’t hold any space in the database and are used to signify the absence of a value or the unknown value in a data field. Some common reasons why…

SQL Stored Procedures An SQL stored procedure is a group of pre-compiled SQL statements (prepared SQL code) that can be reused by simply calling it whenever needed. It can be used to perform a wide range of database operations such as inserting, updating, or deleting data, generating reports, and performing complex calculations. Stored procedures are very useful…

The SQL DEFAULT Constraint The SQL DEFAULT Constraint is used to specify the default value for a column of a table. We usually set default value while creating the table. The default values are treated as the column values if no values are provided while inserting the data, ensuring that the column will always have a value.…

The SQL CHECK Constraint The SQL CHECK constraint is used to add conditions on a column of a table. Once you add the check constraint on a column, it ensures that the data entered into the column meets the specified conditions. If a particular record does not meet the conditions, the database will prevent you from inserting…

SQL NULL functions are used to perform operations on NULL values that are stored in the database tables. A NULL value serves as a placeholder in the database when data is absent or the required information is unavailable. It is a flexible value not associated to any specific data type and can be used in columns of…

The MIN() and MAX() functions in SQL are aggregate functions. They are used to compare values in a set and, retrieve the maximum and minimum values respectively. An aggregate function is a mathematical computation that takes a range of values as input and yields a single value expression, representing the significance of the provided data.…

SQL Hosting SQL Hosting is nothing but a means to manage any RDBMS linked to your website using SQL. If the website has an access to a RDBMS, any data from the website you created will be stored and retrieved from this database. There are various SQL hosting plans available if your web server is…

If you take a user input through a webpage and insert it into an SQL database, there is a chance that you have left yourself wide open for a security issue known as the SQL Injection. This chapter will teach you how to help prevent this from happening and help you secure your scripts and SQL…

SQL Wildcards SQL Wildcards are special characters used as substitutes for one or more characters in a string. They are used with the LIKE operator in SQL, to search for specific patterns in character strings or compare various strings. The LIKE operator in SQL is case-sensitive, so it will only match strings that have the exact…