Database Administrator

MySQL sorting: select order by, mysqlorder SELECT and order by are combined for sorting: The products table is as follows: A is sorted by product name column: B is sorted by multiple columns. The default sorting order is ascending:

Set up Oracle10G (5) for RAC in AIX to install oracle and set up listening. racoracle10g Establish a series of RAC instances under AIX Set up Oracle10G (5) for RAC in AIX to install oracle and set up listening Environment Node Node 1

SQL Server Performance Tuning 4: Writing efficient queries, SQL Server TuningRestrict query rows and columns to improve performance This rule is very simple and will not be detailed here.Use search to optimize the performance by parametric judgment (

Common Database types Int, bigint, smallint, and tinyintUse the exact numeric data type of integer data.BigintInteger Data from-2 ^ 63 (-9223372036854775808) to 2 ^ 63-1 (9223372036854775807) (All numbers ). The storage size is 8 bytes.IntInteger

The connection can be established in the FROM clause or WHERE clause of the SELECT statement. It is similar that it helps to distinguish the connection operation FROM the search conditions in the WHERE clause when the clause points out the

Automatic MSSQL SynchronizationThe following uses 117 and 75 as examples to describe: 117 release & distributor, 75 subscription ServerI. preparations:1. Create a sqlagt user on 117 & 75, which belongs to the administrators group and is used to

IT has been around for a while. At the beginning ''''''The difficulty is mainly in programming languages, arrays, logic, algorithms ,...After these steps, the difficulties will rise to the database design.And Data logic.An excellent system will

When querying users, you may also use a variety of query conditions, such as by employee ID, by name, by gender, or by education level. It is also possible to query by a combination of multiple conditions, such as checking the educational background

The customer has encountered a problem with DG. The storage uses ASM management and has multiple disk disks.When a data file is created in the master database, the data files automatically created in the slave database are in the same disk group,

NoSQL Database: consistent reading of data High ConsistencyAccess any node in the cluster at any time, and the data obtained is consistent; User consistencyFor the same user, the data obtained during cluster access is consistent;Solve user

Linux database instance startup settings 1. Modify/oratab [Root @ org54 ~] # Vi/etc/oratab -- change N to Y, as shown below: # This file is used by ORACLEutilities. It is created by root. sh # And updated by the Database ConfigurationAssistant when

-- User SQL> -- create a user named "grace" whose password is password. The new user does not have any permissions. SQL> create user grace identified by password; Verify the user: password Authentication Method (User Name/password) external

In MySQL, we can store a value or a user-defined variable saved in a query result, and then apply the following statement.SET defines the variable; SET @ var_name: = expr [, @ var_name = expr]...SET @ var_name = expr [, @ var_name = expr]...Note:① ":

By default, MySQL installation on Linux is case sensitive to database tables. The modification is simple. You only need to modify the mysql configuration file. Mysql> show tables;+ -------------------------------------- +| Tables_in_cddl |+ ---------

1. sum over usage Sum (col1) over (partition by col2 order by col3) The above function can be understood as: grouping by col2 (partition), sorting by col3 (order), and continuous addition (sum) Table a has the following content:B C D02 02 102 03 202

N + 1 Problems N + 1 is the most common performance problem in database access. First, let's introduce what N + 1 is: For example, there are two tables in our database: MERs and Orders. Orders contains a foreign key mermer_id pointing to the

In the process of using MySQL DATA, sometimes we need a field that is not the primary key and does not repeat it. In this case, we need to use the SQL UNIQUE constraint. The following is an introduction from w3school: The UNIQUE constraint

Database: Oracle11gr2 Master DatabaseAlter database force logging;Alter system set db_unique_name = 'erpdb' scope = spfile; -- let's make the master database db_name = db_unique_nameAlter system set REMOTE_LOGIN_PASSWORDFILE = EXCLUSIVE scope =

1. When the MySQL installation package of the msi version is last executed, it will die in step 3 and no response will be returned directly. This is because MySQL has been installed on the local machine before and is not uninstalled cleanly,

Building oracle11G DG in linux (2): Building a master database Environment Name Master Database Slave Database Host Name Bjsrv Shsrv Software Version RedHat performanise5.5, Oracle 11g 11.2.0.1 RedHat