Alter Table Set

ALTER alter alter the name of the table structure of the name of the table ALTER TABLE ALTER TABLE ALTER TABLE statement is used to add, modify or delete columns in the existing table. sql alter table syntax To add a column to a table, use the following syntax: alter table table_name add column_name datatype To delete a column in a table, use the following syntax: alter table table _...

Hive in the official document of the query language has a very detailed description, please refer to: http://wiki.apache.org/hadoop/Hive/LanguageManual, most of the content of this article is translated from this page, Some of the things that need to be noted during the use process are added. Create tablecreate [EXTERNAL] TABLE [IF not EXISTS] table_name [col_name data_t ...

Http://www.aliyun.com/zixun/aggregation/13713.html ">hbase is a distributed, column-oriented open source database, rooted in a Google paper BigTable: A distributed storage system of structured data. HBase is an open-source implementation of Google BigTable, using Hadoop HDFs as its file storage system, using Hadoop mapreduce to handle ...

If a computer manufacturer, its database holds machine and accessories product information. The table used to save the whole product information is called pc; the table used to save the parts supply information is called parts. There is a field in the pc table, used to describe the type of CPU used in this computer; there is a field in the parts table, the description of the CPU model, we can think of it as a list of all CPU models. Obviously, the CPU used by this manufacturer must be a model that exists in the supply information sheet. At this time, two tables ...

The complete collection of SQL statement operations deserves to be permanently stored the following statements are part of the MSSQL statement and are not available in Access. SQL classification: ddl-data Definition language (create,alter,drop,declare) dml-Data Manipulation Language (Select,delete,update,insert) dcl-Data Control Language (Grant,revoke, Commit,rollback first, briefly introduce the basic statement: 1, Description: Create number ...

Usually speaking of foreign keys, we only mention "the purpose of the foreign key is to determine the referential integrity of the data." However, what foreign keys specifically include the actions and meanings? 1, set the outer chain: (1), create a foreign key through create table: see 2 lines of code is built in the table command: create table city (... key idx_fk_country_id (country_id), constrain ...

Recently released Hive 0.13 ACID semantic transaction mechanism used to ensure transactional atomicity, consistency and durability at the partition layer, and by opening Zoohttp: //www.aliyun.com/zixun/aggregation/19458.html "> Keeper or in-memory lock mechanism to ensure transaction isolation.Data flow intake, slow changes in dimension, data restatement of these new use cases in the new version has become possible, of course, there are still some deficiencies in the new Hive, Hive ...

Using Lzo compression algorithms in Hadoop reduces the size of the data and the disk read and write time of the data, and Lzo is based on block chunking so that he allows the data to be decomposed into chunk, which is handled in parallel by Hadoop. 　　This feature allows Lzo to become a very handy compression format for Hadoop. Lzo itself is not splitable, so when the data is in text format, the data compressed using Lzo as the job input is a file as a map. But s ...

The following article is mainly about the specific method of implementing a simple and practical optimization of the MySQL database, as well as what specific steps in the actual operation are worthy of our attention. The following article describes the MySQL database is a simple practical optimization of the specific methods to achieve, including how to conduct regular table analysis and inspection, and how to properly optimize the table on a regular basis, the following is a description of the specific program, I hope in your future Learning will be helpful. 1, regular analysis table and checklist analysis table syntax is as follows: ANAL ...

Intermediary trading http://www.aliyun.com/zixun/aggregation/6858.html ">seo diagnose Taobao guest cloud host technology Hall sometimes some of us are too focused on the inner chain of the site and the construction of the outside chain, 　　But ignore the site's most basic internal optimization work, and these optimization work if we do not do a good job, often like building a house, the foundation did not play in prison, think of the house how high and big the same reason! Recently I used ...