Oracle

Grouping Functions , multi-line functions Summary of non-null dataOnly Lieri the null value first.Grouping is not requiredSql> Select COUNT (*), sum (Salary), AVG (Salary), min (Salary), Max (salary) from employees;sql> CREATE TABLE t1 (x int);sql>

=========================oracle Database Simple Statement ============--%type type--sql> declare var_name varchar2 (--zm_tree); Fname%type; Var_type varchar2 (+);--zm_tree. Flinktype%type; Begin SELECT T.fname,t.flinktype to Var_name,var_type from

single-line functionSql> Select Upper (first_name), Lower (last_name), Length (last_name) from employees;Sql> Select (sysdate-hire_date)/7 from employees;Sql> Select Trunc ((sysdate-hire_date)/30, 0) from employees;Sql> Select Trunc (Months_between (

Exporting data using exp and EXPDP1.exp Export Data CommandExp gd_base/@192.168. 13.211 file=d:\export\gd_base.dmp log=d:\export\gd_base.log full=y2.EXPDP Exporting data(1) CMD window to connect to database, go to Sqlplus pageSqlplus Sys/[email

Dual is a virtual table that makes up the syntax rules for SELECT, and Oracle guarantees that there will always be only one record in dual. We can use it to do a lot of things, as follows:1. To view the current user, you can execute the following

We all know that after the Oracle database installation is complete. By default, there are several system roles or permissions. Nomal,sysdba,sysoper Wait, every time you log in to Oracle. are directly logged in as Conn/as sysdba. But I never know

just like completing the JDK installation, you need to configure the environment variable java_home and path for the system to let the system know the Javac command inside the JDK. Similarly, there is a process required to install Oracle. When you

For Oracle's self-increment column, use the serial number (sequence).Initialization phase to manually establish a sequence, and then insert the time, but also to manually read the sequence nextval assigned to the relevant fields, such as ID, the

There are two ways in which JDBC connects to an Oracle database: Connection Database SID Connecting to a database service_name When the SID is connected, the string is as follows:URL="Jdbc:oracle:thin:@192." 168.56. :1521: orcl1

The NVL () function, which handles NULL.Decode () function,: Majority value judgmentDecode (value \ column, Judge value 1, display value 1, Judge value 2, display value 2) If the judgment value is not included, the display is emptyThe Decode ()

Transfer required:EXISTS specifies a subquery to detect the presence of a row. Syntax: EXISTS subqueryParameter: subquery is a restricted SELECT statement (the COMPUTE clause and the INTO keyword are not allowed).Result type: Boolean returns TRUE if

Conceptual Mode: Conceptual mode, also known as pattern, is a description of the global data base structure in the database, and is the public view of the whole user. This description is abstract, does not involve specific hardware environments and

the integrity constraints of data are some constraints on the data description, and three types of integrity constraints can be found in the relational data model: Entity integrity, referential integrity, and user-defined integrity.

1. Merge function wm_concat (column)Wm_concat (column name), which separates the column values by the "," number and displays them as a row. If the column value is in Chinese, choose another way: Wm_concat (to_char (column name))For example, the

I. Oracle monitoring, database, startup and deactivation of Oracle servers Login with root: Switch user su–root/root operating system, generally only the root user has access to the Oracle database server installed in the operating system, and

After 9i, the internal component size of the SGA can be dynamically adjusted or automatically managed by the database, and when the memory size is set, the basic unit of allocation is granularity (granule) granule is a contiguous virtual memory,

D:\install\PLSQL\instantclient_11_2An error occurred while reinstalling Oracle 11g,plsql connection Oracle today:ORA-12154:TNS: Unable to resolve the specified connection identifier. On the internet a rough look, the error is more common, mainly is

1. Dataguard Primary and Standby switching1.1. Check if the current master repository has switching conditions On slave SelectSequence#,first_time,next_time,archived,applied fromV$archived_logwheresequence#=(Select Max(sequence#) fromV$

 in the process of doing the project, a page uses a similar example of the following SQL query data. For the sake of secrecy and ease of use, I replaced the table names and fields in the project with the system tables and fields in the ORACLE

Source of original article (http://blog.csdn.net/lichkui/article/details/4306299)The merge statement is a new syntax for merging the UPDATE and INSERT statements oracle9i. Through the merge statement, the other table is queried based on the join