Learn how the NULL value represents a lack of value and is separate and distinct from zero or a zero-length string.
- [Instructor] NULL is a special state for…a result with no value.…This is necessary because it's often important to…distinguish between a zero value, or an empty string,…or a non-value result.…We're gonna go back to our test.db database here.…The last two movies, we've been working with…a table called Test that we created for…a purpose of learning about…inserting and deleting rows.…So if I say SELECT * FROM test,…you see we get that table.…
Notice the word NULL that appears in…a few cells here in our table.…NULL is a special state in SQL.…It's not really a value, it's the lack of a value,…so you cannot test for it as you would…a normal value with the equals sign…because it has no value.…I cannot do this; this doesn't work.…WHERE a = NULL.…If I try that, you see I don't get any matches…because NULL is not a value.…It's the absence of a value.…
To test for NULL, you need to use a special condition…called IS NULL, like this.…Now I get two rows because there are two rows that…match with a NULL in the A column.…The opposite of IS NULL is IS NOT NULL,…
- 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
2. SQL Overview
3. Fundamental Concepts
7. Dates and Times
Dates and times1m 52s
11. Views and Subselects
12. Defined Functions
13. A Simple CRUD Application
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