Alter Table Unique

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 _...

mysql tutorial to modify the table / field to add / delete table index create table test (blob_col blob, index (blob_col (10))); In mysql 5.1, myisam and innodb table prefix can reach 1000 bytes long. Note that the prefix limit should be measured in bytes, while the prefix length in the create table statement is interpreted as the number of characters. Must be considered when specifying the prefix length for columns that use multi-byte character sets. ...

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 ...

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 ...

The logical design of database is a very broad problem. In this paper, the main key design of the table is discussed in the design of MS SQL Server, and the corresponding solutions are given. Primary key design status and problems about database table primary key design, in general, based on business requirements, based on business logic, the formation of primary key. For example, when sales to record sales, generally need two tables, one is the summary description of the sales list, records such as sales number, the total amount of a class of cases, and the other table record of each commodity ...

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 transaction http://www.aliyun.com/zixun/aggregation/6858.html ">seo diagnose Taobao guest stationmaster buy cloud host technology Hall Yesterday put one of my DZ forum from X2 upgrade to X2.5 appeared a problem, upgrade into a dead cycle, specific hints as follows: update.php?step=waitingdb&nextstep=prepare& sql[...

As an outstanding representative of the Object relational database, Oracle is undoubtedly the most powerful. Whether it's the size of the database, the support of multimedia data types, the parallelism of SQL operations replication, or the security services, Oracle is much stronger than Sybase, Informix, Added to the latest version of the Oracle8.0.4 is to enhance the characteristics of this, but also introduced a number of new features, such as: Data partitioning (partitioning), Object-relational technology (objects relational T ...

The number of mobile devices used worldwide is increasing. Faced with the challenge of creating a good web experience across multiple different devices, there are now a number of solutions. But which of these solutions is most appropriate for any given project? To answer this question, the author of mobile priority, Luke, uses Bagcheck as a case in point (note: Bagcheck is an innovative enterprise engaged in search and discovery), explains the reasons behind choosing to design the mobile and desktop editions separately, and refines the four optimized mobile web products ...

Consumers have always paid special attention to the opinions expressed directly to them. Marketers may spend millions of dollars on well-designed advertising campaigns, but what often makes consumers determined is often simple and free stuff: word-of-mouth recommendations from trusted sources. As consumers face too many product choices no longer ignore the traditional marketing methods of indiscriminate bombing, word of mouth publicity is quietly and effectively stand out. In fact, the first factor behind any decision to make 20% to 50% of all buying decisions is word of mouth. When consumers first purchase ...