WHERE Clause

Quick reference

• 00:05 In the last video, we talked about the select statement.
• 00:07 In this video, I want to expand on the select statement with the where clause.
• 00:12 And the where allows us to create more specific information,
• 00:15 to pull out more specific details.
• 00:17 And it's very easy, we just come down here and type in WHERE, and
• 00:21 then we give it some specific detail that we want.
• 00:23 So let's come up here and change this from all records to, let's go First Name.
• 00:33 And as I start to type, I can tab in order to do that.
• 00:37 And let's go Age, so we want to display the First Name, the Last Name,
• 00:42 and the Age of everybody in our database table,
• 00:46 where First Name is like John.
• 00:51 So if we execute this, we're gonna get an error, cuz we want single quotation marks.
• 00:57 Here we have John Elder and John Smith.
• 01:00 That's as easy as this is.
• 01:03 What can we do here?
• 01:04 I use this like, let me pull up this list.
• 01:07 You can also use these conditional operators, equal, not equal, greater than,
• 01:12 less than, greater than or equal to, less than or equal to, between and like.
• 01:16 Now, between is usually a range,
• 01:18 we wanna say give us everybody with ages between 12 and 25, or whatever.
• 01:23 Like is a pattern search, First Name like John, right.
• 01:28 And you might think why don't I use equal?
• 01:30 So I want the First Name to equal John.
• 01:34 Well if we execute this we get this error, the data types text and
• 01:38 var char are incompatible with equal.
• 01:41 Now if we changed First Name to Age, and
• 01:46 we wanted everyone whose age is 18, John Smith is 18.
• 01:51 If we want everybody whose age is greater than 18, we could get all these.
• 01:58 You'll see, John Smith isn't on this list, because he's only 18.
• 02:02 If we changed this to less than I don't know, let's say 20.
• 02:08 Execute, then get John Smith again.
• 02:11 We could do between, where age between, let's say 30 and 40.
• 02:17 We execute that, John Alder is 39, Steve Jansen is 32.
• 02:24 That's the where clause, very, very useful.
• 02:28 And like I said, you use these equal, not equal, greater than, less than.
• 02:33 If you've taken basic math classes in elementary school, you're
• 02:36 familiar with these equal to and greater than or equal to signs and the between.
• 02:42 You just write it out like this between two number ranges or
• 02:46 the like, as we did earlier.
• 02:48 So, that's the where clause.
• 02:50 In the next video, we'll talk about the and and the or clause.

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