Database Administrator

MySQL Databases can not only be joined between tables, but also can be joined by themselves. This function is quite comfortable. Let's take a look at how to make the table join itself in mysql.Create a table in MySQLCreate table d(Id int (10)

During program debugging, one way is to start from the first line, which is very hard (for example, the program source files are too many or compiled or encrypted ). The other method is to check from the back. The last write is the DB, so we start

1: view memory: grep MemTotal/proc/meminfo View swap: grep SwapTotal/proc/meminfo 2: Check the RPM package. Red Hat Enterprise Linux

Installing Oracle 10 Gb in CentOS 4.6 may cause the following common errors: The preceding error indicates that the Display variable of the X11 Window Server is incorrectly configured. Solution: open a terminal as root and enter "# xhost +" and "#

Oracle locks can be divided into several types: DML lock (data lock), DDL lock (dictionary lock) and internal lock/latch.DML lock can be divided into row lock and table lock. Row lock in select .. for update/insert/update/delete is automatically

When installing Oracle on Linux, the following errors are often reported: You cannot use the command/usr/X11R6/bin/xdpyinfo to automatically check the display color. Check whether the DISPLAY variable is set. You can use the following command to

Because of the differences in Linux versions: the locations and names of automatically started shell scripts are also different. in linux versions such as RedHat and red flag, the startup scripts are placed in/etc/rc. in the d directory, the name is

After Oracle is installed, a database is created and no listening service is found. You can solve this problem by using the following method. Run Net Configuration Assistant and select Add Listener Configuration Configuration items are simple.

During work, we often observe the space release and Application Performance Improvement brought about by index reconstruction. Space release is easy to understand and measure. How much will index reconstruction affect the performance of applications?

Group by function of Oracle The test process is as follows :--- Rollup: Details and summary of employees' salaries in each department for reference.Select t. dept_id, t. dept_name, sum (t. salary)From qcfang. test1 tGroup by rollup (t. dept_id, t.

Oracle Introduction Oracle is the first word for English translation of oracle (Oracle bone inscriptions) Unearthed from Yin. Oracle is the world's largest supplier of information management software and services. It was founded in 1977 and is

I believe everyone is very familiar with the index structure. It is composed of roots, branches, and leaves. Of course, this refers to the common B + tree indexes. We still use the test table in Oracle collection table and column statistics (see.

In Oracle, columns in the table below the sys user cannot be dropped. If drop is performed, an error is returned: SQL> desc test Name Null? Type ----------------------------------------------------------------------------- Id notnull number

Oracle provides the custom type function. You can define the Record and Table based on your own situation. Record data storage is a Record, A record Table is used to store multiple records. If the Record data type Record is a one-dimensional array,

1. After reading the introduction of MemSQL, it took several minutes to browse the website, Read getting started, download, install, and start it. MemSQL http://memsql.com/ Its publicity Slogan is the world's fastest database. your data. ACCELERATED.

UNDO function:1. rollback2. Construct CR blocks to provide read consistency3. rollback: When the instance is restored Undo table empty area status:1. free available rollback segments2. active indicates that there are active uncommitted transaction

After Fedora 19, Fedora replaces mysql with mariadb. Although these two things are the same, I still like mysql, and I don't know why. In Fedora 20 (64bit), I only installed mariadb once, no solution can be found on the Internet. (If anyone knows,

Today, we used the stress test provided by hbase to stress down our hbase cluster. Cluster configuration: master 8 CPU * 32G + 3 8 CPU * 16G Parameter configuration. The zookeeper and hdfs configurations are modified. Test method: Hbase org.

MySQL Binary Log, also known as bin-log, is a Binary Log file generated by mysql execution changes. It has two main functions:* Data Recovery* Master/Slave databases. It is used to add, delete, modify, and maintain synchronization with the master

1. log on to the ASM instance and check whether the ASM disk is correct.[Oracle @ rhel5 ~] $ Export ORACLE_SID = + ASM[Oracle @ rhel5 ~] $ Sqlplus/as sysdbaSQL> select name, state from v $ asm_diskgroup; NAME STATE--------------------------DG1