Your database table may contain a lot of columns. Learn how you can retrieve only a subset of all table columns in your SQL query.
- [Man] In addition to selecting or retrieving all columns…for all rows in a table we can also choose…to only retrieve certain columns.…Imagine that you have a very, very wide table.…It can have 20, 30, 50, a hundred different columns.…You don't always want to return all columns…in your query.…You might be interested in only specific columns.…For example: let's say we want to only retrieve…the first name, last name, and the salary…for the employees in our company from the employees' table.…
So in order to accomplish that,…instead of typing SELECT *…I can just type SELECT first_name,…which is the name of the first column…I want to retrieve in my table.…Note that it's not necessarily…the first column in the table, which is employee ID,…just the first column that I want retrieved…and displayed by my query.…So SELECT first name,…and specify the next column I want to retrieve.…For example: last_name.…
So by typing SELECT first name, last name…from employees, I'm telling Oracle to return only…the first name and last name columns for all rows…
Note: This training course is appropriate for beginning database developers with no prior experience with SQL or Oracle.
- Using Oracle SQL*Developer, the free development environment
- Selecting data from tables
- Filtering data
- Using functions to manipulate data
- Joining data from tables
- Creating tables
- Updating values
- Truncating data
- Grouping and ordering result sets
- Working with primary keys
- Checking constraints
Skill Level Beginner
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1. Introduction to SQL
2. Preparing the Course Environment
Downloading the course VM2m 16s
3. Using Oracle SQL Developer
4. Basic SELECT Queries
5. String, Number, and Date Functions
6. Joining Table Data
7. Manipulating Data
8. Grouping Data
9. Advanced Topics
Next steps1m 33s
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