Learn how you may return only unique rows from your query, removing all duplicates, using the SELECT DISTINCT statement.
- [Instructor] There will be times when you may want to know…all the different values of a column in your result,…without duplication.…For this purpose SQL provides the SELECT DISTINCT statement,…for example if we use the world database,…and I SELECT Continent from Country.…You notice I get 239 rows and many of them are duplicates,…this isn't telling me how different continents there are.…
So for this we have SELECT DISTINCT,…if I say SELECT DISTINCT Continent from Country,…now we only get seven rows,…that's because there's really just a few continents…according to the divisions…using this database there are seven,…and so using the SELECT DISTINCT statement,…you get only unique results.…For another example, let's go to the Exercise File here,…and we'll just copy all of this, and paste it in,…and for this we're gonna use the test database,…and what we have here is a simple table, called test…with two columns, a and b, and they're both integers,…and I add a bunch of rows to this and run select,…and you see we have now this table with 10 rows,…
Author
Bill Weinman
Released
7/2/2018- Understanding SQL terminology and syntax
- Creating new tables
- Inserting and updating data
- Writing basic SQL queries
- Sorting and filtering
- Accessing related tables with JOIN
- Working with strings
- Understanding numeric types
- Using aggregate functions and transactions
- Automating data with triggers
- Creating views
- Defining functions in PHP
Skill Level Beginner
Duration
Views
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Introduction
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Welcome1m 16s
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Exercise files2m 21s
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Course overview1m 38s
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1. Installation
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Installing on Windows: Part II10m 16s
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Installing on a Mac: Part I6m 45s
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Installing on a Mac: Part II12m 10s
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2. SQL Overview
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About the overview3m 39s
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Database organization2m 54s
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The SELECT statement5m 49s
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Selecting rows2m 3s
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Selecting columns1m 29s
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Counting rows2m 42s
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Inserting data3m 9s
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Updating data2m 28s
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Deleting data1m 42s
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3. Fundamental Concepts
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Creating a table3m 40s
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Deleting a table2m 14s
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Inserting rows3m 31s
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Deleting rows1m 55s
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The NULL value5m 22s
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Constraining columns3m 17s
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Changing a schema2m 3s
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ID columns2m 21s
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Filtering data5m 43s
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Removing duplicates2m 37s
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Ordering output2m 23s
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Conditional expressions2m 30s
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4. Relationships
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Understanding JOIN2m 19s
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Accessing related tables4m 31s
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Relating multiple tables4m 27s
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5. Strings
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About SQL strings1m 33s
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Removing spaces2m 26s
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Folding case2m 13s
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6. Numbers
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Numeric types3m 32s
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What type is that value?2m 12s
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Integer division1m 56s
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Rounding numbers1m 2s
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7. Dates and Times
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Dates and times1m 52s
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8. Aggregates
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What are aggregates?4m 38s
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Using aggregate functions1m 57s
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Aggregating DISTINCT values1m 53s
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9. Transactions
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What are transactions?2m 2s
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Data integrity3m 10s
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Performance3m 27s
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10. Triggers
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Preventing updates2m 36s
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Example: Timestamps2m 26s
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11. Views and Subselects
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Creating a subselect3m 47s
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Creating a view3m 32s
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Creating a joined view2m 32s
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12. Defined Functions
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Overview1m 7s
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Defining functions in PHP4m 27s
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13. A Simple CRUD Application
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Embedding SQL4m 50s
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The SELECT functions3m 30s
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Conclusion
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Goodbye1m 3s
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Video: Removing duplicates