What I'm going to do is I'm going to walk you through a very simple table. I'm going to create the table in a Oracle Utility that is called SQL Plus. This is provided by Oracle. It's very widely used. I'm going to create a table called products. I'm going to create it with two columns, productID, that's going to specify a unique number that will identify a row uniquely and a productName. A productID will serve just as a skew would, but it's going to be unique to the table. ProductID will become important later on. ProductName will be the name of the product. Then I will store in the products table. The DDL statement that I'm going to use to accomplish this task, is going to be the create table statement. The way you know it's DDL or data definition language is because it has the word create in it. The other examples of data definition language statements are alter and drop. I'll use all three of them. I will use create, alter, and drop. Alter is change something or modify something, and drop means to delete it. I'm going to create a table called products, and then I'm going to open parentheses over here and down here I'm going to close parentheses. This semicolon means that I'm done with the statement. The semicolon is very important in the Oracle SQL syntax. It signals the end of a statement. These are my column names, productID and productName. Here I'm saying that the productID will be an integer, a whole number essentially, and that the productName will be a variable length character, varchar2, as it's called, with a maximum of 20 characters in the productName, that's what that 20 means. Variable length character means that is going to have up to 20 characters in the productName and no more. It may have five, it may have two, it will have at least one character, and up to 20. That's done. Variable length character part, these are two columns, productID and productName, integer and variable length character, the data type. The name of the table is products. Nice, let's do this. Here is the SQL Plus Utility that I'm logged into already. I'm going to do a create table and I'm going to create a table called products. Open parentheses. I'm going to say productID is going to be an int, and I'm going to say that the productName will be a variable length character2 with a maximum of 20 characters and there's the table created. That's how simple it was. To see that the table got created, I can run the describe command. If I do describe products, it's not case sensitive. As you can see here, I'm describing products. Notice how it's stored, the column names it seemed the way it's an upper case. Here are the data types that is specified, 38 for the maximum number of numbers allowed in a integer data types, that's a lot of numbers and variable length character 20 is a maximum of 20 characters. Just describe the table, semicolon signals the end of the statement. Create a table called products. Opening and closing parentheses tells the DDL create, what I'm going to be specifying as columns for the table. ProductID and productName, specify the data types, comma between the column names, and then data types. Then semicolon after the closed parentheses to signal the end of the statement. Now what that means is, I could have written this whole thing out in one line. Notice how I have it here in four lines, I could have written the whole thing out in one line just by opening and closing parentheses, putting a dark semicolon at the end, specifying the productID and productName with a data type and a comma between the columns. But it just looks neater this way. This is the preferred method of writing it out. This 2, 3, 4, 5 is the number of lines. Create table is the first line. This open parentheses is Line 2, the productID enters Line 3, the productName varchar2 (20) is Line 4, and 5 is the closing parentheses and semicolon. This is very simple, how the table got constructed.
