basic understanding of SQL and to get a feel of how it works. Audience. This tutorial is prepared for beginners to help them understand the basic as well as the. •Execute a basic SELECT statement. •Differentiate between SQL statements and SQL*Plus commands. Lesson Aim. To extract data from the database. you need. SQL, Structured Query Language, is a programming language designed to manage data stored in relational databases. ALTER TABLE lets you add columns to a table in a database. AS is a keyword in SQL that allows you to rename a column or table using an alias.
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This tutorial will give you quick start with SQL. Audience. This reference has been prepared for the beginners to help them understand the basic to advanced. LECTURE OUTLINE. ▫ SQL Data Definition and Data Types. ▫ Specifying Constraints in SQL. ▫ Basic Retrieval Queries in SQL. ▫ Set Operations in SQL. 2. SQL queries use the SELECT statement. □ General form is: SQL query results can be ordered by particular attributes. □ Two main Aggregate Examples.
RUN displays the command or block in the buffer before executing it.
The results of your script are displayed below the Input area by default. Use the History screen to access and rerun commands previously executed in the current session.
SQL Cheat Sheet
If you use the History screen to re-execute a script, you may get different results from those previously obtained, depending on the current system variable values.
When you are done, press Return to move to the next line.
Press Return or click Execute. Sometimes, the result from a query will not fit the available page width. See Setting Page Dimensions.
Displaying Foreign Keys Foreign keys link one table to another — they are attributes in one table which refer to the primary key of another table. The list of defined triggers can be viewed using the following query.
Displaying Internal Tables Internal tables are formed as a by-product of a user-action and are usually not accessible. The data in internal tables cannot be manipulated; however, the metadata of the internal tables can be viewed using the following query.
Displaying a List of Procedures A stored procedure is a group of SQL queries that logically form a single unit and perform a particular task. Swapping the Values of Two Columns in a table In this and subsequent examples, we will use a common company database including several tables which are easily visualized.
Our practice DB will include a Customers table and an Order table. With this in mind, we can easily imagine an Orders table which likewise contains the indexed customer ID field, along with details of each order placed by the customer.
In our first one of SQL examples, imagine a situation where the zip and phone fields were transposed and all the phone numbers were erroneously entered into the zip code field. Returning a Column of Unique Values Now, suppose that our data entry operator added the same Customers to the Customers table more than once by mistake.
As you know, proper indexing requires that the key field contain only unique values. Between Monday and Tuesday Today is Wednesday, and we arrive at work and discover that our new data entry clerk in training has entered all new orders incorrectly on Monday and Tuesday.
NULL values can be inserted in the following ways: Implicitly by omitting column from column list. BETWEEN operator is used to display rows based on a range of values in a row whereas the IN condition operator is used to check for values contained in a specific set of values.
Examples in Each Chapter
Why are SQL functions used? SQL functions are used for the following purposes: To perform some calculations on the data To modify individual data items To manipulate the output To format dates and numbers To convert the data types Q What do you mean by recursive stored procedure?
Recursive stored procedure refers to a stored procedure which calls by itself until it reaches some boundary condition. This recursive function or procedure helps the programmers to use the same set of code n number of times.
SQL clause helps to limit the result set by providing a condition to the query.
A clause helps to filter the rows from the entire set of records. Apart from this SQL Interview Questions Blog, if you want to get trained from professionals on this technology, you can opt for a structured training from edureka! Click below to know more.
Following are the ways in which dynamic SQL can be executed: Write a query with parameters. Using EXEC.
What are the various levels of constraints?Find a degree that fits your goals. NULL values can be inserted in the following ways: Implicitly by omitting column from column list. You will also be able to: Networking Technician: Already registered? What are Views used for?