Joins are an important part of the SQL language allowing you to combine the data of two, or more, tables in a single SQL statement. Learn about the concepts of joins and the various types of joins supported in the Oracle database such as LEFT JOIN, RIGHT
- [Instructor] The SQL join clause allows us to combine recommend codes from two tables. A join in SQL locates related column values across two or more tables. So for example, assume that we have an employees table as well as a departments table. And lets say, in our example, we would like to retrieve the employee ID, employee name. But instead of retrieving the department number from the employee table, which makes little sense.
I mean, what's department 20, right? So assuming that instead of retrieving the department number we want to retrieve the department name. But the department name column exists in the departments table, not in the employees table. Using a SQL join, we can choose which column links both tables together, department number in our case. And produce a unified result, combining data from the two tables together.
So in our case we can choose to display the employee ID and employee name from the employees table but display the department name from the departments table. We will see joins in action throughout this chapter so don't worry if it all seems a little bit to theoretical for now. Also note that there are multiple types of joins you can use in your SQL quarries. These include inner joins, left joins, right joins, and full outer joins.
Inner joins will select records that have matching values in both tables. Left join will select records from the first table with any matching records from the right table. A right join selects records from the second that is right most table, with matching rows from the left most table. And a full outer join selects all records that match from in the left or right tables. So don't sweat it. We'll see all of this in action throughout our chapter.
Author
Released
1/17/2018Note: 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
Duration
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Introduction
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Welcome1m 37s
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1. Introduction to SQL
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What is SQL?2m 30s
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Database tables2m 21s
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Overview of table data types4m 21s
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SQL query structure4m 38s
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2. Preparing the Course Environment
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Downloading the course VM2m 16s
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3. Using Oracle SQL Developer
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Exploring database objects1m 29s
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Filtering specific objects1m 25s
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Using SQL Developer tabs2m 18s
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Viewing query output1m 18s
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4. Basic SELECT Queries
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Using WHERE to filter dates2m 42s
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Using column aliases2m 18s
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Using ORDER BY3m 29s
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5. String, Number, and Date Functions
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Introduction to functions1m 39s
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Using LENGTH1m 4s
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Using CONCAT4m 48s
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Using LOWER and UPPER2m 44s
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Using INSTR4m 32s
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Using RPAD and LPAD3m 31s
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Using ROUND1m 15s
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Using TRUNC1m 36s
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Using SYSDATE1m 59s
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Using SYSTIMESTAMP1m 37s
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Using MONTHS_BETWEEN3m 2s
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Using ADD_MONTHS1m 17s
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6. Joining Table Data
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Joining data from tables4m 12s
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INNER JOIN1m 17s
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LEFT JOIN2m 55s
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RIGHT JOIN1m 55s
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FULL OUTER JOIN1m 59s
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7. Manipulating Data
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Creating a simple table2m 1s
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COMMIT and ROLLBACK2m 23s
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Introduction to transactions3m 43s
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Deleting rows for a table3m 23s
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Updating values2m 40s
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8. Grouping Data
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Using aggregate functions2m 24s
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Using GROUP BY2m 45s
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Using HAVING3m
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9. Advanced Topics
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Primary keys2m 47s
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NOT NULL constraints1m 36s
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Check constraints3m 2s
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Foreign key constraints6m 4s
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Subqueries4m 39s
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Conclusion
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Next steps1m 33s
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Video: Introduction to SQL joins