Oracle

--oracle implement self-increment id--create a T _studentinfo table The CREATE TABLE t_studentinfo ("id" integer NOT NULL primary key, Xsname NVARCHAR2 (+) NOT NULL, Xsage integer NOT NULL, Mobile varchar (n), Email varchar (+), Address

In oracle 12th, the group by statement is used, and the group by rollup, decode, grouping, nvl, nvl2, nullif, RATIO_TO_REPORT statements are used. 1.DecodeSimilar to stream data statements such as if... then, case... when... Decode(Condition, value 1

This article mainly introduces the usage of Oracle merge into. For more information, see In many cases, the following situation occurs: if a piece of data already exists in the table, update it. If it does not exist, insert new data. if you do not

A trigger is a special type of subroutine stored in a database. It cannot be called directly by users, but is automatically triggered by the system when a specific event or operation occurs. Call execution. The trigger cannot accept parameters.

1. Regular Expression of question 3rd Regular Expressions only search, replace, format, and other functions. Regular Expressions are usually used for back-reference formatting. length and concatenate are not calculated. 2. Delete columns with

Error reported by scott user set autotrace onSCOTT @ TEST0422> set autotrace onSP2-0618:Cannot find the Session Identifier. CheckPLUSTRACERole is enabledSP2-0611: Error enabling STATISTICS reportSCOTT @ TEST0422> conn/as sysdbaConnected. SYS @ TEST04

If you accidentally overwrite the previous stored procedure, You have to flash back quickly. The longer the duration, the less likely it will be to flash back. The principle is very simple. The definition of a stored procedure is a data dictionary.

Oracle optimized or replaced with in, exists, and union statements. There is no problem in testing! Select the appropriate statement based on the actual situation! If there is an index, or full table scan, in and not in should also be used with

In PL/SQL programs, cursors are often used for transactions that process multiple rows of records. When a query statement or data manipulation statement is executed, a set of records may be generated or processed. A cursor is a memory area allocated

From the table above, we can see that a database is composed of multiple tablespaces, one tablespace is composed of multiple segments, and one segment is composed of multiple partitions (extent) A zone is composed of multiple blocks. Store it

Environment: win7_x64, oracle11g Description: The connection fails on the first day of the first day; 2: pl SQL developer Connection Tool, self-installed oracle database, and installed Client 3: oracle clients are not required when oracle is

A pos system has a large application volume and a large data volume! Statistical analysis of historical transactions affects another application to a certain extent. The two applications are OLTP and OLAP respectively. In fact, many projects have

1. Create your own VARCHAR2ARRAY type CREATE OR REPLACE TYPE "VARCHAR2ARRAY" as table of varchar2(300); 2. Create the function SPLITSTR Create or replace function "SPLITSTR" (p_str IN VARCHAR2, p_delimiter IN VARCHAR2) RETURN varchar2array IS/***

I. ORACLE physical architecture Explanations: PGA: private memory zone, which is only used by the initiator. After a user logs on, the information is saved in PGA. If the memory is not enough, oracle will complete it in the temporary

I. Users View the default tablespace of the current user SQL> select username, default_tablespace from user_users; View the role of the current user SQL> select * from user_role_privs; View the system and table-level permissions of the current

1. Think about the problem In a table, an id column (integer) exists. When a user wants to add a record, this column will automatically grow from 1. How can this problem be solved? 2. Introduction Oracle uses sequence processing to automatically

In the OLTP system, nested connections account for about 70%, hash connections account for 20%, and merge sorted connections account for 10%.Nested connection Algorithm: Nested join selects a small table as the driver table from two tables, and a

JMYBJS = (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP) (HOST = 129.1.9.90) (PORT = 1521 )) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = jmybjs) ) ) Create a folder on disk D: D: \ backup \ dmp D: \ backup \ log Used to store dmp files and

Limited result set In Oracle, it is very useful to use the ROWNUM field. Generally, you can use it to do two things: 1. Execute the top-N query. This is similar to the LIMIT Syntax of other databases. (Search for the first n pieces of data) 2.

1: executed per minute Interval => TRUNC (sysdate, 'mi') + 1/(24*60) Or Interval = & gt; sysdate + 1/1440 2: daily scheduled execution Example: Execute at every day Interval => TRUNC (sysdate) + 1 + 1/(24) 3: scheduled weekly execution