[untitled] gbase 8s V8 8 SQL Guide: tutorial-6

6 Write advanced SELECT sentence  
In this chapter, the use of SELECT The range of operations that the statement can perform . And enables you to perform more complex database queries
Inquiry and data processing . To write SELECT The statement focuses on SELECT Five clauses in sentence grammar . This chapter adds
GROUP BY Clause and HAVING Clause . Can be GROUP BY Clause is used in conjunction with aggregate functions to organize
FROM The row returned by the clause . Can include HAVING Clause GROUP BY Clause returns a value setting bar
Pieces of .
This chapter also extends the earlier discussion of connectivity . It illustrates self connection （ It enables you to connect the table to itself ） And four
Type of external connection （ In which the keyword is applied OUTER To handle two or more connected tables in different ways ）.
This chapter also introduces related and unrelated subqueries and their operation keywords , Shows how to use UNION Operator to group
Combined query . And defined what is called Union 、 Set operation of intersection and difference .
The examples in this chapter show how to use... In queries SELECT Part or all of a sentence . Clause must be as follows
Sequential display
1. Projection
2. FROM
3. WHERE 
4. GROUP BY
5. HAVING
6. ORDER BY
7. INTO TEMP
About using all these clauses in the correct order SELECT Examples of statements , Please refer to the picture 5.
additional SELECT Sentences INTO （ Can be used in SQL API Specify the program and main variables in ） stay SQL Programming
And the publications provided with the product .
This chapter also describes nested SELECT sentence , The sub query is in the of the main query Projection 、FROM or WHERE 
Clause . Description of other sections SELECT Statement how to define and manipulate a collection , And how to query results
Set operations .