oracle sql practice exercises

Oracle optimizations are generally divided into:1. SQL Optimization (Oracle now performs the necessary optimizations based on SQL statements, which should not be user-like, but must be and affect performance as correlated and nested queries)A, the condition of the SQL statem

Oracle is a large database with a C/SClient/Server structure. It is mainly used in the 4GLSQL language and has the advantages of being powerful, simple, and easy to learn. The working process of the C/S structure is: when the client c end) inputs and sends an SQL statement, it will be sent to the server S end through the network ), the result is analyzed and executed, and then returned to the client through

Label:In practice, the tables in SQL Server need to be imported into Oracle. It is no problem to have previously tried DTS directly with SQL Server. But this time because of the amount of data in tens, so reported insufficient virtual memory. Finally, the solution is to export the TXT file and the

Label: I'm going to talk about a problem here. Added a header file to the practice example#include And then I can't compile, I always say I can't find oraca.h.And then I changed it.EXEC SQL INCLUDE Oraca;This will be the successful compilation of the past.First dynamic SQL statement: Non-query statement with no host variableThe application receives

Tags: Oracle object-oriented reportingSome Oracle SQL required for reportingThe cold, stay at home and read the mastering Oracle SQL 2nd, found that Oracle is still very powerful, there are 200 light functions, those object-orient

perform organizational connections in the memory. Finally, we would like to discuss the subquery unnested feature. In most cases, we think that Oracle can generate better execution plans. However, in practice, we have also found many such scenarios: The subquery speed is very fast and the data volume is small, but the speed is slow after the connection. The result is that the subquery in the execution plan

Tags: des ar io using SP strong on Data divSome Oracle SQL required for reportingThe cold, stay at home and read the mastering Oracle SQL 2nd, found that Oracle is still very powerful, there are 200 light functions, those object-oriented query language is difficult to emulat

execution plans. However, in practice we have also found a lot of such scenarios: sub-query speed, the amount of data is not small, but the slow after the connection, the result is to find the execution plan subquery is opened.By default, Oracle has a "small compute" feature when estimating the number of result sets for a multi-conditional statement. That is, the estimated number of result sets is less tha

than the published book of its kind. The whole book is driven by a comprehensive human resources project, not only can the various theoretical knowledge points well into practice, but also allow the reader to experience the complete process of the project, "explaining more practice" is also an important feature of the books, to ensure that the reader can really learn. Of course, the most important thing is

.) You can use records to retrieve information from the returning clause of DML statements. It is usually useful to keep a local copy when updating data for subsequent PL/SQL operations. Before Release 2, we can use the returning clause to store data somewhere after computation and call are complete. In Release 2, data can be stored in a record. For example, the following is the practice before release 2

access|js|oracle|server|sqlserver| Access | data | Database access Oracle, SQL Server, DB2, Informix, Access database in JSP Now have a lot of novice JSP users will often ask the database how to connect ah, how old mistakes ah? So I concentrated in this write an article for your reference, in fact, this database logic all put in the JSP may not be a good

oracle| optimization 1. The statements that have been validated are exactly the same as those already in the shared pool 2. Variable names as consistent as possible 3. Rational use of outer joins 4. Use fewer layers of nesting 5. Multi-use concurrency The optimization steps for a statement are generally: 1. The SGA area is adjusted so that the SGA area is optimally used. 2. optimization of the SQL statemen

; (Select max (userid) from (Select top10 UserId from UserInfo order by UserId)) Method 4 (only available in Sqlserver 2005 ): Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->Select * from (select row_number () over (Order by UserId) as RowId, * from UserInfo) UWhere U. RowId between 10 and 20 In SQL Server, there are several other writing methods, not one by one. In the four methods, the last two

; (Select max (userid) from (Select Top10 userid from userinfo order by userid)) Method 4 (only available in sqlserver 2005 ): Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->Select * from (select row_number () over (Order by userid) as rowid, * From userinfo) uWhere U. rowid between 10 and 20 In SQL Server, there are several other writing methods, not one by one. In the four methods, the last two me

and), whose attributes are similar to char, and in practice it is generally used instead of the non-portable numeric data type. SeparatorCHAR, datetime, Interval, numeric EXTERNAL fields can be identified by using delimiters, and the syntax for delimiters is as follows: Terminated by and enclosed by can be used alone, or can be used together, here are some examples: TERMINATED by ', ' a data string, enclosed by ' ', '

variable.When the others then exception-handling statement. --Executes the statement (written at the end) when the exception number that is thrown does not exist in the exception statement block.End5. Custom exception: implemented by defining a new Exception class in Java. Implemented by exception numbers in Oracle.1 Eclare2N Number (1);3 V_error exception;4 begin5Dbms_output.put_line (' Throw a single exception