tuning oracle sql queries

Tags: RAC ORACL table structure Operations Direct format FFFFFF text formatted outputVideo lesson: Li Xinghua Oracle from Getting started to mastering video lessonsLearner: Sun Luo nuoVideo Source: 51CTO College If you want to query, you must use the query part of the DML support, relative to the simple query, the popular understanding is that all records are queried, but you can control the display of the column through the syntax. The

Oracle technology _ 5 minutes will use stored procedure _ simple instances of stored procedure (including loops, conditions, addition and modification queries, parameter input, variable assignment, java calls, etc) Example business functions: 1. query the data in PROCEDURE_TEST_A table and PROCEDURE_TEST_A_SUB table based on the input type A_TYPE and display the main content. 2. query the PROCEDURE_TEST_A t

, only 50 pieces of data will be displayed, and 10 thousand pieces of data will be re-checked during page turning, and another 50 pieces of data will be displayed. The following paging SQL statements are common. SQL server also has a version that uses the top keyword. Remember how to use rownum between minvalue and maxvalue when I first learned oracle. Like the

8600, respectively), so this SQL statement is called a single-row subquery. Note: external queries and internal queries can get data from different tables. Using group functions in subqueries SELECT from Employees WHERE = (SELECTMIN fromYou can display data from the main query by using group functions in a subquery to return a single line. The sub

Oracle queries the department with the minimum number of employees [SQL] -- department table create table t_dept (d_id number primary key, d_name varchar2 (20); create sequence dept_sequence start with 1 increment by 1; www.2cto.com -- employee table create table t_emp (e_id number primary key, d_id number references t_dept (d_id), e_name varchar2 (20); create se

, lang from t2;1 chinese 1 english 2 chinese 2 1 english After connect: Select emp, mgr, lang from t2Start with emp = 1Connect by prior emp = mgr;1 chinese 2 chinese 2 1 english 1 english 2 chinese 2 1 english Lang = 'China' after filtering: 1 chinese 2 chinese 2 chinese Repeated rows are obviously not the expected results. 7) CONNECT BY LEVEL Next, let's take a look at a special usage of connect by level. This is a headache, but it is also very useful in some situations: Select LEVEL from

Tags: result rom query using combined query execution environment equals on outputThe execution environment of a statement is a SQL window of Plsql, which is intended to determine the number of records not equal to a field from all tables in the entire database.The code is as follows:DECLARE S_sql clob:= "; --Declares a variable that is used to store the SQL statement of the queryV_citycode varchar2 (20); -

toexecutes two successive queries, and uses the result of the first query as the search value in the second query. Child query syntax ? Execute the subquery (internal query) before executing the main query (externalquery). ? The primary query uses the results of the subquery.SELECT select_list from table WHERE expr operator (SELECT select_list from table); A subquery is a SELECT statement that is embedded in the clause of another SELE

The most important thing about Oracle tree queries is the Select...start with ... prior syntax. Depending on the syntax, we can list a table-shaped structure in the order of the tree. Below is a list of common query methods for tree queries in Oracle, as well as the frequently used

Installing more CPUs on a separate server is a current trend. With symmetric multi-processor (SMP), it is not surprising that an Oracle server has 8, 16 or 32 CPUs and several gigabytes of RAM.Oracle has been following the pace of hardware development, providing a number of features that are geared toward multiple CPUs. Starting with Oracle8i, Oracle implements parallelism in each database function, includi

database table SELECT * from Dba_tab_columns; SELECT * from All_tab_columns; SELECT * from User_tab_columns; SELECT * from Dba_tab_cols; SELECT * from All_tab_cols; SELECT * from User_tab_cols;25. Querying database table columns for comments SELECT * from Dba_tab_comments; SELECT * from All_tab_comments; SELECT * from User_tab_comments;26. View the run schedule for the query Explain plan for SELECT * from Dict; SELECT * FROM table (dbms_xplan.display); Continuous update ... -----------------