The Language of SQL- P14 docx

... covered some of the quirks of sorting, particularly when it comes to data with NULL values and with numbers in character columns. At the start of the chapter, we mentioned some of the general ... Sequences In the previous examples, all of the data is character data, consisting of letters from A to Z. There are no numbers or special characters. Additionally, there has b...

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... ‘7/2/2009’) 5 Looking at the values in the above chart, you can see that the month of 7/2/2009 is 7. The day is 2. The week is 27, because 7/2/2009 is in the 27th week of the year. The weekday is 5 because ... elements as the day or week of the date. Again, the name of this function differs, depending on the database . In Microsoft SQL Server, this function is...

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... order to apply the needed logic. The simple format only works with an analysis of a single column. Due to the inherent complexity of IF-THEN-ELSE logic, the CASE expression is one ofthemorechallengingtopicsinthisbook.Inthischapter,wehavefocusedon using CASE ... task of selecting a subset of rows. The logic utilized for the WHERE keyword builds on the column-based logic s...

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... rows that are selected, and then it returns a count of the number of rows. In the second format of the COUNT function, a specific column is specified rather than the asterisk. Here’s an example: SELECT COUNT ... statements. In the first, you’re merely counting rows where the GradeType equals ‘‘Homework.’’ There are three of these rows. In the second, you’re counting occu...

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... view of the Personnel table and the EmployeeID column of the Managers view of the table. In other words, the indicated manager is also an employee. Notice that Susan Ford isn’t shown in the previous ... Bland The trickiest part of this SELECT is the ON clause in the join. To get the self join to work correctly, we need to use the ON to establish a relationship be...

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... create a view of the table for those users. You can then use the security features of your database to grant access to the new view for those users, while restricting them from accessing the underlying ... Orders.OrderID ¼ Refunds.OrderID The only item missing in the above CREATE VIEW is the ORDER BY clause of the original SELECT statement. Since views aren’t stored as p...

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... to retrieve data. The concept of combining queries is often referred to as set logic , a term taken from mathematics. Each SELECT query can be referred to as a set of data. The set logic we will ... the SELECT columnlist. In other words, after the subquery is evaluated, it returns a single value, which is then included in the columnlist. Here’s a general format of the above...

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... joins, subqueries, views, and the like, you’ll grapple with the reality of raw data and learn how to manipulate it with a few twists of logic. But logic isn’t the end of the matter. The language of SQL plays ... but within the realm of computer languages, the language has a certain aesthetic appeal. Looking Ahead 213 Figure 20.3 Pivot table. The important point a...

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... OS is a registered trademark of Apple Inc. PostgreSQL is a trademark of PostgreSQL Inc and the Regents of the University of California. Allothertrademarksarethepropertyoftheirrespectiveowners. Allimages†CengageLearningunlessotherwisenoted. LibraryofCongressControlNumber:2010925128 ISBN-13:978-1-4354-5751-5 ISBN-10:1-4354-5751-X Course ... Lisa The Language of SQL Larry Rocko...

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... The AND Operator 72 The OR Operator 73 Using Parentheses 73 Multiple Sets of Parentheses 75 The NOT Operator 76 The BETWEEN Operator 79 The IN Operator 80 Boolean Logic ... area of expertise is with data warehouse systems and reporting tools. He recently developed a suite of BI tools for ASA P Software, a subsidiary of Dell Inc. He holds an MBA from the University of Chi...

Ngày tải lên: 05/07/2014, 05:20