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View the primary key of a table in a library, identify columns, computed columns, field types, allow nulls, default values, and other properties SELECT [Table name]= Case whent.column_id= 1 Then object_nameT.object_id)ELSE "' END , [Field Number]=t.column_id,[Field name]=T.name,[PRIMA
sql| Difference |varchar| field type What is the difference between nvarchar and varchar in SQL Server 2000? SQL Server provides two types of data to store character information. The two data types are roughly the same in how they are used in SQL Server or applications. The difference is that nvarchar is used to store Unicode data that handles multilingual data
The following table summarizes the data types of all available fields in Microsoft Access, their usage, and storage space. Data Type Usage Big and small "Text"(Text) A combination of text or numbers, such as an address or a number that does not need to be calculated, such as a telephone number, part number, or zip code. It can contain a maximum of 255 characters.Microsoft Access only saves characters in the
the VARCHAR2 (n) type in Oracle is only used to hold smaller strings, where n is less than 4000, so in this case, It is best to use a fixed-length char (n) type that corresponds to Oracle's VARCHAR2 (n), which not only improves efficiency but also saves storage space, and is best used with the allocate parameter if the varchar (n) type is used, which improves the performance of the database. It can reduce the input/output operation between memory and hard disk.To pay attention to the string Chi
This article will implement the CAML invocation of JQuery AJAX for the custom fields in SharePoint 2007 in two ways. respectively: 1, the traditional way of writing code, with Fldtypes_ your field type. XML, build custom field types. 2, using Jianyi spcamleditor tool, directly modify the CAML of a list of fields. The former is highly reusable, and the latter i
default Charset=utf8;mysql> insert INTO Stu (Name,gender) VALUES ("Zhang San", "male"); When you add data, you don't need to add registered field information anymore.Note: When data is modified for a datetime type, the time does not change, and the timestamp type changes, for example:Mysql> CREATE TABLE Stu (ID int unsigned NOT NULL Auto_increment primary key,Name varchar (5) is not NULL,Gender enum ("Male", "female"),Registered timestamp//timestamp
choiceSummarize:Use GUIDs. There is no duplication problem, and data merging is very simple. The association speed is slower than int. It is best to use this scenario for frequently merging data or offline input data online uploads.The GUID value is random and does not accept any form that can be more meaningful to the user. There is no way to determine the order in which the GUID values are generated, so it is not suitable for existing applications that increment index key values in the loop o
how many bytes are required to define the double type. MySQL strictly controls the data in each column of the table, this is the key to the success of data-driven applications. MySQL provides a set of data types that can be assigned to each column in the Table. Each type forces data to meet a set of pre-determined rules for this data type, such as the size, type, and format. Here we will summarize the data types
There is a table named TB, field segment named Name, data type nchar (20).1. Assuming that the field data is empty, you can do it directly, regardless of the field type you are changing to:ALTER TABLE TB Modify (name Nvarchar2 (20));2, if the field has data, then to NVARCHAR2 (20) can be directly executed:ALTER TABLE T
At that time, I used the latest MySQL version 5.6.14 for testing. I did not find anything special. Later I developed a problem in using the decimal field type and cannot insert it. Type of decimal field in MySQL 5.6.14 At that time, I used the latest MySQL version 5.6.14 for testing. I did not find anything special. Later I developed a problem in using the decimal fiel
Oracle Common database field typesCommon database field types are as follows: Field type Chinese description restrictions other description CHAR fixed length string max length bytes VARCHAR2 variable length string maximum length 4000 bytes can do index maximum length 749 NCHAR by character Set fixed length string maxim
clear, be sure to read this article, but also in the future reconstruction of the work of the correction, otherwise, sooner or later, the problem will come to your side. second, the way to reconstruct the tableLet's not talk about the other, just the way to rebuild the table. As follows 1, to ensure that all table fields, field types, and lengths are exactly the same, I generally do not recommend using t
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 inconsiste
field value is only in English, you can select varchar. If the field value contains many double-byte (Chinese, Korean, etc.) characters, use nvarchar. Differences between char varchar nvarcharOnline help:In general, if it contains Chinese characters, use nchar/nvarchar. If it contains English letters and numbers, use char/varchar. ** A good summaryMany developers often do not consider the char and varchar
the same length is almost the same (as described later) 3. The length of varchar does not affect the processing speed !!! (See the following explanation) 4. The total length of a column in an index can be up to 900 bytes. Therefore, nchar cannot create an index for varchar, char, and nvarchar with a length greater than 900. 5. indexes cannot be created on text or ntext. 6. In O/R Mapping, the attribute types of the corresponding entities are generall
(Entity, ColumnName, Rs.getarray (i));BreakCase Types.BIGINT:classFactory.setprop (Entity, ColumnName, Rs.getint (i));BreakCase Types.BINARY:classFactory.setprop (Entity, ColumnName, Rs.getbinarystream (i));BreakCase Types.BLOB:classFactory.setprop (Entity, ColumnName, Rs.getblob (i));BreakCase Types.CHAR:classFactory.setprop (Entity, ColumnName, rs.getstring (i));BreakCase Types.INTEGER:classFactory.setprop (Entity, ColumnName, Rs.getint (i));BreakCase Types.DOUBLE:classFactory.setprop (Entity
There are two Field Types in MySQL that are confusing, namely TEXT and BLOB. In particular, the bloggers who write their own blog programs do not know whether to change their blog body fields to TEXT or BLOB. The following are some differences: 1. The main difference between TEXT and BLOB is that BLOB stores binary data and TEXT stores character data. Currently There are two
specified length, it is automatically filled with spaces behind it, make the length reach the corresponding length. If there is a var prefix, it indicates that the actual storage space is longer, for example, varchar and nvarchar variable-length data will not be filled with spaces, text storage is also variable length. Unicode or non-Unicode: in a database, only one byte is required for English characters. However, two bytes are required for Chinese characters and many other non-English charact
Note: Source Network Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/--> -- ========================================================== ============================== -- Lists All SQL Server tables, field names, primary keys, types, lengths, decimal places, and other information. -- Run in the query analyzer. -- ========================================
setBrithday (Date brithday) {this. brithday = brithday;} public Gender getGender () {return gender;} public void setGender (Gender gender) {this. gender = gender ;}}Enumeration class:Package learn. jpa. bean;/***** @ doc Gender enumeration type **/public enum Gender {MAN, WOMEN ;}Note:1. TemporalType. DATE indicates the DATE format, for example2. TemporalType. TIME indicates the TIME format. Example: 12: 21: 343. TemporalType. TIMESTAMP indicates the date plus time format. Example: 12:21:34@ En
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