oracle sql for dummies

the number of buffers at a time.Bytes % Total BufferGets/Total Buffer Gets} SQL ordered byReads:} Records the top SQL statements that occupy the total Disk Physical reads (physical IO). Note that the execution of this SQL statement accounts for the total Disk Physical reads within the monitoring scope, instead of the Disk Physical reads occupied by a single

The ORACLE tutorial is: Comparison between Oracle and SQL Server in enterprise applications. My company not only owns Oracle databases but also SQL Server databases, so I often encounter two problems that people ask me.The first is usually "can you teach me how to use

The following articles mainly introduce Oracle installation, configuration, and SQL * Plus operation steps. I saw Oracle installation, configuration, and SQL * Plus operation steps on the relevant website two days ago, I think it's good. I just want to share it with you. I hope this will help you in your future studies

; NUL --- Abc SQL> select concat (null, 'abc') from dual; CON --- Abc SQL> select null + 10 from dual; NULL + 10 ---------- 5. null-related function rules Oracle has functions such as nvl, nvl2, nullif, and coalesce to handle null. 5.1 nvl (expr1, expr2) Description: If expr1 is null, expr2 is used as the return value. If it is not null, expr1.expr1 and

A course design is required to study Oracle database application technology this semester. PowerDesigner export SQL, import to Oracle to query the table structure reports ldquo; ORA-04043: A course design is required to study Oracle database application technology this semester. PowerDesigner export

This article describes how to set the shortcut keys for PLSQL in Oracle databases, including setting MyObjects, remembering the password, and double-clicking the display table by default. This article describes how to set the shortcut keys for PL/SQL in Oracle databases, including setting My Objects, remembering the password, and double-clicking the display table

wait time CLUSTER_WAIT_TIME NUMBER Cluster wait time USER_IO_WAIT_TIME NUMBER User I/O Wait Time PLSQL_EXEC_TIME NUMBER PL/SQL execution time JAVA_EXEC_TIME NUMBER Java execution time ROWS_PROCESSED NUMBER Total number of rows processed on behalf of this SQL statement COMMAND_TYPE NUMBER

SQL> show all -- View all 68 system variable values SQL> show user -- display the current connected user SQL> show error -- Display error SQL> set heading off -- disable the output column title. The default value is ON. SQL> set feedback off -- disable counting feedback of t

Oracle SQL optimization notes Notes for writing Basic SQL statements Use the in operator as few as possible. Basically, all in operators can be replaced by exists. You can use not exists or external join + instead of the not in operator. When Oracle executes the in subquery, it first executes the subquery, puts th

; --Rollback segment statisticsSELECT * from V$pwfile_users; --Privileged User informationSELECT * from V$sqlarea; --The resources and related information accessed by the currently queried SQL statementSELECT * from V$sql; --basic information about the same as V$sqlareaSELECT * from V$sysstat; --Database System state information --the more commonly used view at the beginning of a session isSELECT * from Ses

strings from the above. Any comparison operation with NULL, such as Summary table of judgment and comparison rules Example: Usage: SQL> select 1 from dual where null = null; No records found SQL> select 1 from dual where null = "'; No records found SQL> select 1 from dual where ''= ''; No records found SQL> select 1

How can I convert Oracle queries to queries in the SQL database? The following describes how to convert an Oracle query to an SQL query. If you are interested in Oracle query, take a look. Oracle's TO_CHAR function can convert the n-bit NUMBER data type to the VARCHAR2 data

1. Choose the appropriate Oracle Optimizer There are 3 Oracle optimizer types: A. Rule (rule-based) b. Cost (based on costs) c. CHOOSE (optional) Set the default optimizer to pass various declarations of optimizer_mode parameters in the Init.ora file, such as Rule,cost,choose,all_rows,first_rows. You will of course overwrite it at the SQL sentence level or at

1. static sqlsql and dynamic SQLOracle compiled PL/SQL program block is divided into two kinds: first, the previous early binding, that is, the SQL statement was established during the program compilation, most of the compilation is this type, and the other is the late-stage (late binding), That is, the SQL statement can only be established at run time, for examp

Oracle databases differ significantly from MSSQL data operations, but there is an analogy in image operations. This article describes how MSSQL database images are implemented in Oracle databases. What are the differences between them.First, the image database in Microsoft SQL database is similar to the backup database in Ora