英文字典中文字典


英文字典中文字典51ZiDian.com



中文字典辞典   英文字典 a   b   c   d   e   f   g   h   i   j   k   l   m   n   o   p   q   r   s   t   u   v   w   x   y   z       







请输入英文单字，中文词皆可：

SQL    
结构式查询语言

结构式查询语言

/S Q L/ An industry-standard
language for creating, updating and, querying {relational
database management systems}.

SQL was developed by {IBM} in the 1970s for use in {System R}.
It is the {de facto standard} as well as being an {ISO} and
{ANSI} {standard}. It is often embedded in general purpose
programming languages.

The first SQL standard, in 1986, provided basic language
constructs for defining and manipulating {tables} of data; a
revision in 1989 added language extensions for {referential
integrity} and generalised {integrity} {constraints}. Another
revision in 1992 provided facilities for {schema} manipulation
and {data administration}, as well as substantial enhancements
for data definition and data manipulation.

Development is currently underway to enhance SQL into a
computationally complete language for the definition and
management of {persistent}, complex objects. This includes:
generalisation and specialisation hierarchies, {multiple
inheritance}, user defined {data types}, {triggers} and
{assertions}, support for {knowledge based systems},
{recursive query expressions}, and additional data
administration tools. It also includes the specification of
{abstract data types} (ADTs), object identifiers, {methods},
{inheritance}, {polymorphism}, {encapsulation}, and all of the
other facilities normally associated with object data
management.

The emerging {SQL3} standard is expected to be complete in
1998.

According to Allen G. Taylor, SQL does __not__ stand for
"Structured Query Language". That, like "SEQUEL" (and its
pronunciation /see'kw*l/), was just another unofficial name
for a precursor of SQL. However, the IBM SQL Reference manual
for DB2 and Craig Mullins's "DB2 Developer's Guide" say SQL
__does__ stand for "Structured Query Language".

{SQL Standards (http://jcc.com/sql_stnd.html)}.

{An SQL parser
(ftp://ftp.ora.com/published/oreilly/nutshell/lexyacc/)} is
described in "Lex & Yacc", by Levine, Mason & Brown published
by O'Reilly.

{The 1995 SQL Reunion: People, Projects, and Politics
(http://mcjones.org/System_R/SQL_Reunion_95/)}.

["A Guide to the SQL Standard", C.J. Date, A-W 1987].

["SQL for Dummies", Allen G. Taylor, IDG Books Worldwide].

(2005-11-17)


请选择你想看的字典辞典：
单词字典翻译
sql查看　sql　在百度字典中的解释百度英翻中〔查看〕
sql查看　sql　在Google字典中的解释Google英翻中〔查看〕
sql查看　sql　在Yahoo字典中的解释Yahoo英翻中〔查看〕

安装中文字典英文字典查询工具!


中文字典英文字典工具:
选择颜色:
输入中英文单字

































































英文字典中文字典相关资料:


  • Difference Between != and lt; gt; for Not Equal in SQL - Baeldung
    When writing SQL queries, we often need to filter out specific values by using a not equal condition However, two different operators are available for this purpose: != and <> In this tutorial, we’ll examine which operator to use and whether they behave differently across various databases
  • SQL NOT EQUAL Operator - GeeksforGeeks
    Let's look at some examples of the NOT EQUAL Operator in SQL, and understand its working First, we will create a demo SQL database and table on which we will use the NOT EQUAL operator
  • Should I use != or lt; gt; for not equal in T-SQL? - Stack Overflow
    '<>' is from the SQL-92 standard and '!=' is a proprietary T-SQL operator It's available in other databases as well, but since it isn't standard you have to take it on a case-by-case basis
  • Not Equal To) (Transact-SQL) - SQL Server | Microsoft Learn
    Compares two expressions (a comparison operator) When you compare nonnull expressions, the result is TRUE if the left operand is not equal to the right operand; otherwise, the result is FALSE
  • MySQL not equal to operator - w3resource
    The WHERE clause is used to filter the rows based on multiple conditions The comparison operator != (not equal to) is used to select rows where the publication language is not equal to "English" The IN operator is used to specify a list of values for which rows should be selected
  • SQL NOT EQUAL Examples
    Learn about writing TSQL statements using the not equal operator along with various examples of using not equals
  • 9. 2. Comparison Functions and Operators - PostgreSQL
    <> is the standard SQL notation for “not equal” != is an alias, which is converted to <> at a very early stage of parsing Hence, it is not possible to implement != and <> operators that do different things
  • SQL Operators - W3Schools
    SQL operators are keywords and symbols used to perform operations with data values SQL operators is categorized into the following types: Exercise? What is this? Which SQL operator is used to add two numbers?
  • Comparison operators - Snowflake Documentation
    Comparison operators are used to test the equality of two input expressions They are typically used in the WHERE clause of a query
  • SQL NOT EQUAL Operator: A Beginners Guide - DataCamp
    The SQL NOT EQUAL operator (<> or !=) filters data by excluding rows that match a specific condition It is commonly used to retrieve data that does not meet the specified criteria in a query





中文字典-英文字典  2005-2009