mainframe database types

Whether in a small, free database space or a large e-commerce site, a reasonable design of the table structure, the full use of space is very necessary. This requires us to have a good understanding of the common data types of database systems. Below I will write a little of my experience to share with you. One, the number type The number

The Date, DateTime, and TimeStamp types in the MySQL database are related. This article describes their features and how they are similar and different. The DATETIME type is used when you need to include both the date and time information. MySQL retrieves and displays DATETIME values in 'yyyy-MM-DD HH: MM: SS' format, the supported range is '2017-01-01 00:00:00 'to '2017-12-31 23:59:59 '. ("Supported" mean

Risks of incorrect selection of Oracle Database Design Field Types An Oracle data type is inaccurate. We will construct a table storage date field, a storage varchar2 field, and a storage date field for a test. I have also written the following: Problems caused by inconsistent field type design and actual business SQL> drop table test purge;SQL> create table test as selectTo_char (to_date ('1970-01-01 ', 'y

Third, indexIn the previous chapter we learned to use explain to generate a query execution plan (QEP) to find the problem with the statement. Of the results returned by explain, three are index-related (possible key, key, extra), and the visible index has a prominent position in improving query efficiency.In this chapter, we will explain in all directions how to use the index to optimize our database.1. Role of the IndexThe principle of indexing is t

I chose byte[] [email protected]Just start using the Java.sql.Blob, will upload the picture GetBytes () after the Hibernate.getlobcreator (Hibernatesessionfactory.getsession ()). Createblob (New byte[] (Pic.getbytes ()));To get the BLOB type.You can actually get the BLOB type (Oracle. BLOB), but it needs to be obtained by means of the Resultset.getblob () of the result set obtained by the original data source and statement.Because using hibernatetemplate or HQL statements, you don't know how to

Tags: type brackets unique order Chinese word breaker query files multiple columnsImprove query speed, facilitate sorting and grouping. (The process of sorting and grouping, if not indexed, results in temporary tables and filesort)Based on business logic, analyze the frequency and order of column queries, and build indexes and composite indexes.Primary key index (primary key),----> No index name is required because there is only one primary key indexUnique index (single key)---->unique Key Email

, Withscores=false, score_cast_func=float) Gets the element of the ordered collection of name corresponding to the index range　　　　# 参数：# name，redis的name# start，有序集合索引起始位置（非分数）# end，有序集合索引结束位置（非分数）# desc，排序规则，默认按照分数从小到大排序# withscores，是否获取元素的分数，默认只获取元素的值# score_cast_func，对分数进行数据转换的函数6) Zrank (name, value) gets the rank of a value in the ordered set of name (starting from 0) 7) zrem (name, values) removes the value of the ordered collection of name corresponding to the member of Values 9) Zremrange

) smembers (name) gets all the members of the collection that the name corresponds to9) smove (SRC, DST, value) move a member from one collection to another collectionSpop (name) removes a member from the right (tail) of the collection and returns itOne) srandmember (name, numbers) randomly gets numbers elements from the collection corresponding to nameSrem (name, values) removes certain values from the collection that corresponds to nameSunion (keys, *args) gets the set of one more name corresp

Label:declare @tablename nvarchar (80)declare @cloumn nvarchar (80)declare @sql nvarchar (400)DECLARE c1 cursor Scroll forSelect Table_name,column_name from Information_schema.columns where data_type= ' datetime 'Open C1Fetch first from C1 to @tablename, @cloumnWhile @ @fetch_status =0BeginSet @sql = ' Update ' + @tablename + ' Set ' + @cloumn + ' =dateadd (yy,10, ' + @cloumn + ') where ' + @cloumn + ' is not NULL ';EXEC (@sql)FETCH NEXT from C1 to @tablename, @cloumnEndClose C1Iterate over all

Char, varchar, nchar, and nvarchar differences for string fields in the program, SQLServer has char, varchar, nchar, and nvarchar types to match (text and ntext are not considered for the time being ), during database creation, these four types are often vague. Here is a comparison. Fixed Length or variable length: the so-called fixed length is fixed length Char,

There are usually many data types in the database and different classification methods. For example, the most common numeric, numeric, and datetime types are also uncommon Boolean, enumeration, and set types. To support a specific data type (such as the simplest INTEGER) in DBMS, we can consider the following aspects.

, with a decimal point followed by 307 zeros. The storage space occupied by float and double types is 4 bytes and 8 bytes respectively. If you need to use decimal fields, the precision is not high, of course, float is used! But to be honest, how does our "Civil" data require high accuracy? I have never used these two types so far-I have not encountered any examples that are suitable for using them. The mos

The data types and sizes in the database store are different. Some places store only numeric types, some store only text types, and some both. Many databases support a variety of specialized types: date and time types, binary char

When creating a table from Django's ORM, we need to define our own classes. When defining a class, he has a wide variety of field types, each with its own parameters to configure, and a simple summary below.First look at the type of field. Although Python offers nearly 20 types, after he transforms into a database table, it is essentially 4

will never catch up with the speed of File System Processing Database Backup has become huge and time-consuming Access to files must go through your application layer and database layer. The last two are real killers. Store thumbnail images in the database? Well, you can't use nginx or other types of lightweight se

can be divided into three types: § Offline backup § Backup and Log Retention § Logical backup Offline backup Only create database backup. Simple backup is suitable for read-only databases or databases filled with batch jobs that can be easily re-created, or databases that do not need to be maintained between backups. Data loss: all changes made after the last backup operation will be lost. This type of rec

most widely used are Sybase 10 and syabse for SCO Unix.Features of the Sybase database:(1) It is a database based on the client/server architecture.(2) It is a truly open database.(3) It is a high-performance database.5.db2DB2 is a database management system embedded in IBM

, with a decimal point followed by 307 zeros. The storage space occupied by float and double types is 4 bytes and 8 bytes respectively. If you need to use decimal fields, the precision is not high, of course, float is used! But to be honest, how does our "Civil" data require high accuracy? I have never used these two types so far-I have not encountered any examples that are suitable for using them. The most

about 2.22E-308 (0.000 ...). 0222, the decimal number of 307 0 after the decimal point. The float type and double type occupy storage space of 4 bytes and 8 bytes respectively. If you need to use a decimal field, the precision is not high, of course, with float! But to say the truth, we "civil" data, which has the requirement of precision so high? These two types have not been used so far-I have not yet encountered cases that are appropriate for usin

The following articles mainly introduce three different types of JDBC drivers in Oracle databases. We all know that jdbc drivers in Oracle mainly include the following three types: 1. jdbc oci: oci is the abbreviation of Oracle call interface, which is similar to the traditional ODBC driver. Because it requires Oracle Call Interface and Net8, it needs to install the client software on the machine that runs