Database Administrator

Syntax for SUBSTRING: SUBSTRING(expression, start, length)Expression String, binary string, text, image, column, or expression that contains a column. Do not use expressions that contain aggregate functions. Start An integer or expression that can

A role is a set of related permissions. The main purpose of a role is to simplify permission management. Once the permissions of this set exceed the minimum requirements of users, it may bring security risks to the database. Role password Test In

SQL> select * from test; 121. Restore SQL by SCN> select * from sys. smon_scn_time order by time_dp desc;30970780The relationship between scn and time: every five minutes, the system generates a system time tag matching with scn and stores it in the

In recent years, with the increasing popularity of big data, the importance of non-relational databases has been recognized by more and more people, and more developers have gradually joined the NoSQL camp. We know that NoSQL means Not Only SQL. In

XML query in SQL SERVER: FOR XML specifies RAWPreface In SQL SERVER, you can specify RAW, AUTO, EXPLICIT, and PATH for XML queries. This article uses some examples to introduce the specified raw xml query in SQL SERVER. Basic for xml query View

Machine mac book, virtualbox4.3.6, and virtualbox are installed with ipvt13.10. In the multi-point distribution environment, After configuring a machine, clone the other two machines. There are three machines in total.1. Configure the

Connect C ++/C to the MySQL database in Linux (3) -- Process returned data 1. Number of fields in the returned result set Unsigned int mysql_field_count (MYSQL * connection); // use the value of MYSQL_ROW as an array that stores a row of

In GPDB, the Master and each Segment Instance have their own postgresql. conf files. ParametersThe number of local parameters means that each Segment Instance is obtained according to its own postgresql. conf file.Take the value of the parameter.

Sometimes, your SQL statements run normally in SQL server, but they do not work in jsp files. It is very likely that the symbol problem is different from. Have you noticed the difference?   String SQL = "select medals. medal, medals. event, medals.

Pure dry goods: WourdCount program example: describes in detail the difference between MapReduce Block + Split + Shuffle + Map + Reduce and the data processing process. The Shuffle process is the core of MapReduce and focuses on the most critical

Partitioned indexes are classified into global indexes and local indexes. Local indexes can be divided into prefix indexes and nonprefix indexes. Currently, global indexes only support indexes with a prefix. Both the B-tree index and the bitmap

I. Partition definition: A partitioned table divides data from a large table into many small subsets, which are called partitions. Ii. Advantages of partitioning: 1. Enhanced availability: If a partition in the table cannot be used due to system

PERCENTILE_CONT and PERCENTILE_DISC in SQL SERVER PERCENTILE_CONT and PERCENTILE_DISC Check the following SQL statements: WITH testas( select N'LeeWhoeeUniversity' as name,10 as score UNION ALL select N'LeeWhoeeUniversity',20 UNION ALL

In Windows, Oracle backs up data every night through EXP and retains the backup data for ten days. 1. Create the backup script oraclebackup. bat Contents: @ Echo offEcho deletes the backup file and log 10 days ago. Forfiles/p "E: \ oraclebackup"/

The developer writes a view. It takes 30 minutes for the select statement to be optimized. The view is as follows:Create algorithm = undefined SQL SECURITY DEFINER VIEW view_offer_labelSELECT ol. OFFER_ID AS OFFER_ID, ol. interval tive_date AS

1. Enable the binary log Configuration: In Windows, if you want to configure directory location for mysql's my. ini log-bin and so on, assume that you want to configure the log of log-bin to the mysqllog file of disk D as binlog. The configuration

Run the following command in CMD:Net stop Net start Note: the default value is mysql. That is:Net stop mysqlNet start mysql Note: How to view the service name: On the desktop, right-click "computer", select "manage", and select "service"

I still remember the feeling of reading tianshu when I read database system principles for the first time, and the cloud was in the fog. Now I have read this book for the second time, and I suddenly felt something, "Oh, it turned out to be like this

I haven't written anything for a long time. I have been reading some open-source things. Next I will post the installation and configuration of ipvs on linux and the reference for using dblink for readers and their future reference: 1, download

I. Data Types 1. Integer Data Type Storage space Description Value Range TINYINT 1 byte Very small integer Signed value:-128 ~ 127Unsigned value: 0 ~ 255 SMALLINT 2 bytes