`
文章列表
Chapter 2 SQL Execution     SQL的执行 Karen Morton   (page51)     You likely learned the mechanics of writing basic SQL in a relatively short period of time. Over the course of a few weeks or few months, you became comfortable with the general statement structure and syntax, how t ...
     7.10 GROUP BY的限制   (page 217)     Your study of GROUP BY would be incomplete without considering what it cannot do.  The list of restrictions placed on GROUP BY is not very long.  The restrictions are listed in the Oracle 11.2 SQL  Language Reference for Oracle 11.2. For example: •  LOB co ...
 7.9 GROUPING SETS and ROLLUP()       (page 214)     There is yet another method that may be used to obtain the results seen in the previous two examples.  The GROUPING SETS() extension to GROUP BY made its debut with Oracle 9i.  The entire GROUP BY … HAVING clause of the previous example can b ...
    7.8 Extending Reports With GROUPING_ID() 使用GROUPING_ID()扩展报告   (page210)     The GROUPING_ID()function is relatively new compared to the GROUPING() function, having been introduced in Oracle 9i, and is somewhat similar to the GROUPING() function.  Whereas GROUPING() evaluates the expression ...
7.7Extending Reports with GROUPING()  用GROUPING()函数扩展报告    (page209)     Another use of GROUPING() is in the HAVING clause, where it can be used to control which aggregation levels appear in the output. The report seen in previous examples creates about five pages of output, which may be more th ...
7.6 Eliminate NULLs with the GROUPING() Function  用GROUPING()函数消除NULL值  (page 207)     There seems to be a problem with the output from the new query seen in Listing 7-12.  While the numbers match the earlier query that used the UNION ALL operator, some of the rows have NULL values for the CUS ...
 7.5 Putting CUBE to work      CUBE实战     (page 201)        When teaching us a new word in fourth grade English class, Mrs. Draper would say, “Now use it in a sentence.”   Much like that, you now need to put the CUBE extension to practical use.  It was fun to see what i ...
7.3“New” GROUP BY Functionality “新”GROUP BY 功能              (page 197)     At times, it’s necessary to write SQL that appears as unruly as the convoluted example in Listing 7-5 so that the desired output can be obtained.  The need for writing such unwieldy SQL has become much less frequent due ...
7.2 HAVING Clause     HAVING 子句   (page 195)     Results generated by GROUP BY may be restricted by the criteria found in the HAVING clause.  The HAVING clause is quite versatile, resembling the WHERE clause in the conditions that may be used. Functions, operators, and subqueries may all be used i ...
Chapter 7 Advanced Grouping  第七章 高级分组    Jared Still    (page 213)     The GROUP BY clause is a venerable member of the SQL statement family.  After learning basic SELECT statements, it is one of first specialized parts of SQL that many practitioners cut their teeth on when learning to create a ...
Using Plan Information for Solving Problems 使用计划信息解决问题 (Page 180)      Now that you know how to access the various bits of information, what do you do with them?  The plan information, particularly the plan statistics, helps you confirm how the plan is performing.  You can use the information to d ...
Understanding DBMS_XPLAN in Detail 深入理解DBMS_XPLAN   (Page 174)     The DBMS_XPLAN package is supplied by Oracle and can be used to simplify the retrieval and display of plan output, as I have demonstrated.  In order to use all the procedures and functions in this package fully, you’ll need to have ...
Identifying SQL Statements for Later Plan Retrieval    标示SQL语句便于之后计划检索 (page 171)     If you want to retrieve a statement that was executed in the past, you can retrieve the SQL_ID and CHILD_NUMBER from V$SQL as demonstrated in Listing 6-7.  To simplify finding the correct statement identifiers ...
Collecting the Plan Statistics  收集计划的统计(信息) (page 168)     The plan operations shown when no plan statistics are available is essentially the same as the output from EXPLAIN PLAN.  To get to the heart of how well the plan worked, you need the plan’s rowsource execution statistics.  These value ...
Execution Plans   执行计划 (page 166)      The actual execution plan for a SQL statement is produced when a statement is executed.  After the statement is hard parsed, the plan that is chosen is stored in the library cache for later reuse.  The plan operations can be viewed by querying V$SQL_PLAN.  V$S ...
Global site tag (gtag.js) - Google Analytics