• SQL

    SQL Constraints

    SQL constraints the data that can be in a table. A violation of a constraint causes an action to be aborted. Constraints can be defined upon creation or using the ALTER TABLE statement once created. The general syntax of a CREATE (or use ALTER instead of CREATE) when defining constraints is as follows: CREATE TABLE tablename ( columnname datatype(size) constraintname, columnname datatype(size) constraintname, columnname datatype(size) constraintname, columnname datatype(size) constraint name, columnname datatype(size) constraint name, ); Obviously, replace columnname with the name of each of your column, datatype with the types of data your column contains and constraint name with the constraint you wish to use. You have the following constraints…

  • SQL

    Create A SQL Database

    So you’re ready to write some software? Or test some cool stuff. Or build something awesome. You can use the CREATE DATABASE statement to get started, by creating a database. To do so is pretty easy, simply run that statement followed by a name for the database (called Customers): CREATE DATABASE Customers; Once you’ve created a database, it’s time to create tables, which can be done using the CREATE TABLE statement. The Syntax of that statement looks something like this, defining a set of columns, their data type and the size of the column (in the form of a maximum length), all wrapped in parenthesis with each column separated by…