Database Administrator

I went to an interview with two cool Internet companies a few days ago and encountered problems in SQL. Well, unfortunately, let's take a look at it. Score 1. Use group Group by Dimension For example: Calculate the total score of each

The preceding two figures show the normal operation of scott user and test data after inserting c ~~~ Start the process.   1. Start -- run -- cmd   Input: sqlplus/as sysdba connecting to database 2. Create a c # scott user CREATE USER c##scott

Once the database is restored, open reports an error ORA-00349, as shown below. Finally, delete the log group. SQL> alter database open resetlogs; alter database open resetlogs * ERROR at line 1: ORA-00349: failure obtaining block size for '+ fra_kg0

1. the following error is reported during Mysqldump: 2014-05-05 14:12:37 7f004a9a2700 InnoDB: Error: Table "mysql". "innodb_table_stats" not found. However, show tables indicates that it exists: But the show create table innodb_index_stats; error

Background: It's fairly common for businesses to want to provide some high availability for their SQL Server databases, and one option is to have two SQL Server databases on separate machines with a SQL Server database mirrored. microsoft provides

1.1 symptom description Failed to allocate shared memory in Oracle. The ALTER log displays the following error message. Errors in file /oracle/db/diag/rdbms/ora01/ora01/trace/ora01_reco_233670.trc: ORA-00604: error occurred at recursive SQL level

Zookeeper _ Id and ObjectIdThe document stored in MongoDB must have a "_ id" key. The value of this key can be of any type and is an ObjectId object by default.In a set, each set has a unique "_ id" value to ensure that each document in the set is

MongoDB stores images and other files in two ways (This article is intended for users who can use MONGODB to integrate Spring) 1. Use Template /*** Storage file ** @ param collectionName collection name * @ param file * @ param fileid file id * @

Welcome to: Northwestern University of Technology-big data and Knowledge Management Laboratory (Northwestern Polytechnical University-BigData and Knowledge Management Lab. Note: (1) experiment environment. Three servers: test165, test62, and test63.

Functions can be used to complete a series of operations. The difference between databases is that the support for functions is different. The learning function of this note. Functions are divided into single-row functions and multi-row functions.

 Exp/imp environment variable character set Conversion Note: ensure that the client encoding is the same as the database encoding to avoid character conversion. Other methods ensure that the exp client encoding is the same as the imp client

1. Add a default comment when creating a table Create table groups (gid int primary key AUTO_INCREMENT COMMENT 'Set primary key auto-incrementing', gname VARCHAR (200) COMMENT 'column COMMENT ',) COMMENT = 'table COMMENT' 2. Modify the created table

Yesterday, my colleague said that a test database could not be logged on. After logging on with PLSQL Developer, the following message is displayed: ERROR:ORA-00604: error occurred at recursive SQL level 1ORA-01653: unable to extend table SYS. AUD $

Hive is a Hadoop-based data warehouse platform. Hive provides SQL-like query languages. Hive data is stored in HDFS. Generally, user-submitted queries are converted into MapReduce jobs by Hive and submitted to Hadoop for running. We started from

A large amount of test data needs to be inserted into the sqlite database and the transaction is intended to be inserted cyclically. However, sqlite does not support the definition of the declare variable, so it cannot be achieved by defining the

To create a table partition, follow these steps:1. Create a master tableCreate table users (uid int not null primary key, name varchar (20 ));2. Create a partition table (the primary table above must be inherited) Create table users_0 (check (uid> =

One Limit of UNION is that the columns generated by two SQL statements must be of the same data type. In addition, when we use the UNION command, we only see different data values (similar to select distinct ). Union only Concatenates the two

(1) For complex data service-level constraints across multiple tables, triggers can be used to replace a large number of background judgment codes, which is highly efficient and convenient.(2) If you want to use a trigger to assist the business

For more blog posts, please note: Children without umbrellas must keep running.(Www.xuchanggang.cn) I. Xtrabackup Overview:Xtrabackup is a mysql database backup tool provided by percona and supports online hot backup. according to the official

Single-line functions-character Functions Although each database supports SQL statements, each database also has operation functions supported by each database. These are single-row functions. If you want to develop a database, in addition to SQL,