What is SQL?
SQL is short for “Structured Query Language.” SQL was developed in the 1970s to query data from relational databases. It is a programming language made up of two parts: Data Definition Language (DDL), and Data Manipulation Language (DML). DDL is used to create or modify relational schema, for example relating university department to an offered course. DML is used to retrieve or modify data in a schema. SQL is centered around set theory and establishing joins between different sets of data.
Relational database management systems, powered by languages like SQL, are useful in many cases. A simple example would be a database of student information at a university. Each student might have an ID number, a log-in, a password, a date of birth, and GPA, among other data points. Each entry must have a unique entry acting as an identifying primary key, in this case, it would be the ID number. Establishing this data set would appear as below.
The ‘not null’ indicates the field must be filled, ‘varchar(128)’ indicates alphanumeric input, and unique indicates the attribute or combination thereof must be unique in the data set. Beginning with a simple database like this, multiple sets of data can be used, referencing one another. A database can be searched for information about certain students, filter out students by GPA or age, and more. The student database can be cross referenced with registering for university classes, or classes can be associated with faculty information, creating information for payroll, financial, or other statistical analysis.
SQL queries can be used to easily retrieve and filter data from a database. It is established as a standard for all database relational schemes. A database must be simple to create, read, update, and even delete. Having information is useless if there is no good way to analyze or access it.
References
INFO 210, Professor Michelle W. Purcell, Drexel University, Winter 2016.
Comments
Ronald Herazo
Ronald, it was very interesting to learn about these different conceptual schemes for how databases work. Relational databases are the framework for how SQL works. I was curious as to what a flat database is in comparison. Also, are there any downsides to using a relational structure versus an object oriented one?
Ray Powell
Ray explains where databases are used in design offices. They are what informs the use of BIM practices. Storing material information, its energy performance, ‘green’ factors, in addition to dimensions and finishes, are what makes modelling so valuable. It allows for lower propagation of errors, is more easily updated, and helps inform more complex life cycle analyses of projects.
Kerry Vogler
Kerry shows how databases can be useful to the construction industry. Databases are important in most businesses, whether the details are handled in house or outsourced is another manner. The first thing that I can think of is payroll. There is a significant amount of information in everyone’s tallied weekly hours that determines how clients are billed, and how subcontractors are paid. There is also security issue of billing information and bank accounts being handled by the software of choice. I agree with you that databases can be hugely useful for contractors, especially in creating estimates, as these can vary greatly by region and productivity of individual team.
Paulina,
ReplyDeleteGreat blog post explaining SQL and the use of SQL in database management. I have used SQL briefly before but you did a great job of explaining it in greater detail. I like how you had example code in your post and went on to explain it. Have you ever used SQL before? And if so what challenges have you had with using it?