The Language of SQL- P29 doc

... the primary table, even if there is no match in the secondary table. The right join is simply the reverse of the left join, switching the order of the primary and secondary tables. Finally, the ... creates a virtual view of the table, in the sense that we can now view this table from two different perspectives. The second main topic of the next chapter will ext...

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... result: The Answer the apple The LTRIM function enables you to get rid of the spaces to the left of ‘ the apple.’’ Note that LTRIM is smart enough not to eliminate spaces in the middle of a phrase. ... spaces, either on the left or on the right side of a value. The LTRIM function ‘‘trims’’ characters from the left side of a character. For example: SELECT LTRIM (...

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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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... 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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... 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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... the order of values after the VALUES keyword corresponds to the order of columns liste d in the columnlist after the INSERT TO. The order in which the columns are listed does not have to be the ... number of times) The columns in columnlist need to correspond to the columns in RowValues. Also, if all the columns in columnlist are listed in the same order as they...

Ngày tải lên: 05/07/2014, 05:20