blocks|key|4502904|text|​|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4502905|📷|atomic|offset|length|4502906|4502907|有关详细信息，请转到此链接。http://ecomputernotes.com/database-system/rdbms/relational-algebra-and-relational-calculus|4502908|[|4502909|4502910|4502911|4502912|4502913|4502914|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/8812cc47b7f7e78b327955ed53c2f458.jpeg|imageAlt|1|LINK|MUTABLE|url|http://ecomputernotes.com/database-system/rdbms/relational-algebra-and-relational-calculus|2|https://ask.qcloudimg.com/http-save/yehe-900000/ee440977189ef6a77642779afae1d399.png|3|https://ask.qcloudimg.com/http-save/yehe-900000/559f256ae6088006511874fc5da4bdfb.png^0|0|0|1|0|0|0|E|2I|1|0|0|0|1|2|0|0|0|0|1|3|0|0^^$0|@$1|2|3|4|5|6|7|18|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|19|8|@]|9|@$E|1A|F|1B|1|1C]]|A|$]]|$1|G|3|4|5|6|7|1D|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|1E|8|@]|9|@$E|1F|F|1G|1|1H]]|A|$]]|$1|J|3|K|5|6|7|1I|8|@]|9|@]|A|$]]|$1|L|3|C|5|D|7|1J|8|@]|9|@$E|1K|F|1L|1|1M]]|A|$]]|$1|M|3|4|5|6|7|1N|8|@]|9|@]|A|$]]|$1|N|3|4|5|6|7|1O|8|@]|9|@]|A|$]]|$1|O|3|C|5|D|7|1P|8|@]|9|@$E|1Q|F|1R|1|1S]]|A|$]]|$1|P|3|4|5|6|7|1T|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|1U|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|X|Y|-4]]|Z|$5|10|U|11|A|$12|13]]|14|$5|T|U|V|A|$W|15|Y|-4]]|16|$5|T|U|V|A|$W|17|Y|-4]]]]

<a href="https://i.stack.imgur.com/exDMX.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/exDMX.jpg" alt="Comparison Between Relational Algebra and Relational Calculus"></a>

go to this link for detail.
<a href="http://ecomputernotes.com/database-system/rdbms/relational-algebra-and-relational-calculus" rel="noreferrer">http://ecomputernotes.com/database-system/rdbms/relational-algebra-and-relational-calculus</a>

[<img src="https://i.stack.imgur.com/VroOK.png" alt="2]">

<a href="https://i.stack.imgur.com/vWBmH.png" rel="noreferrer"><img src="https://i.stack.imgur.com/vWBmH.png" alt="enter image description here"></a>

blocks|key|1812641|text|纽约大学一个班级的This演讲对我很有帮助。我也只是在学习这一点，所以我不能提供太多的帮助，但我至少知道关系代数处理更具体的集合表达式，连接操作和集合组合，而关系演算主要坚持AND-OR关系和存在(“存在一个x这样的条件(X))或通用的(”对于所有x的，条件(X))量词。我设想关系代数表达式在功能和特性上类似于汇编语言，而关系演算表达式在外观和功能上更接近于高级编程语言。希望这能对你有所帮助。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1812642|entityMap|0|LINK|mutability|MUTABLE|url|http://www.nyu.edu/classes/jcf/CSCI-GA.2433-001/slides/session5/RelationalAlgebra-RelationalCalculus-SQL.pdf^0|9|4|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

<a href="http://www.nyu.edu/classes/jcf/CSCI-GA.2433-001/slides/session5/RelationalAlgebra-RelationalCalculus-SQL.pdf" rel="nofollow">This</a> presentation from an NYU class was pretty helpful to me. I'm just learning this as well so I can't be of too much assistance, but I at least know that relational algebra deals with more specific set expressions, join operations, and set combinations while relational calculus mostly sticks to AND-OR relations and either the existential ("There exists an x such that [condition(x)]) or the universal ("For all x's, [condition(x)]) quantifiers. I imagine relational algebraic expressions to be similar to an assembly language in functionality and specificity while relational calculus expressions are closer to a high-level programming language, in appearance and functionality. Hope this helps some.

blocks|key|5918511|text|TL;DR:查询调用RA+(关系代数)运算符&两个关系演算(+RC)+TRC+(元组RC)和DRC+(域RC)的查询对于同一事物是不同的语法:关系值或关系值的元组必须满足的属性/条件。SQL也是(它们的混合体)。谓词演算是数学、逻辑、科学(包括计算机科学)和工程(包括软件工程)中的精确语言。而RA是过程性的，RCs是声明性的，这是一个神话。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|5918512|5918513|关系包含的元组使一些谓词--由属性参数化的语句模板--成为一个真正的命题--语句。|5918514|/*+tuples+where+employee+PERSONNAME+lives+on+STREET+in+CITY+*/
Employee
/*+tuples+where+employee+PERSONNAME+works+at+COMPANY+for+$SALARY+*/
WorksFor|code-block|syntax|javascript|5918515|RA风格的查询表达式包括属性名称、关系变量/常量名称、关系文字(涉及属性名称和值)和关系运算符。运算符有JOIN、UNION、MINUS、PROJECT、RESTRICT等。它表示通过计算表达式获得的关系值。但它也是价值要满足的要求。|5918516|/*+RA+query+for+tuples+where
++++FOR+SOME+STREET+&+CITY+[employee+PERSONNAME+lives+on+STREET+in+CITY]
AND+NOT+FOR+SOME+COMPANY+&+SALARY
++++++++[employee+PERSONNAME+works+at+COMPANY+for+$SALARY+AND+COMPANY+=+'FBC']
*/
++++PROJECT+PERSONNAME+(Employee)
MINUS+PROJECT+PERSONNAME+(RESTRICT+COMPANY+=+'FBC'+(WorksFor))|5918517|对于关系值，RC表达式为set-builder+notation。它涉及一个带有关系变量/常量名称、属性名称和值、谓词操作符和量化名称(逻辑变量)的谓词。运算符是AND、OR、NOT、FOR+SOME/ALL和=。它通常被视为满足价值的要求。但它也表示通过计算表达式或某个等价表达式而获得的关系值。|5918518|DRC具有作为属性的量化名称。对于每个属性只有一个参数的语句，我们使用一个简写：|5918519|Employee(PERSONNAME,+STREET,+CITY)
++++means+(PERSONNAME,+STREET,+CITY)+IN+Employee
++++means+employee+PERSONNAME+lives+on+STREET+in+CITY
WorksFor(PERSONNAME,+COMPANY,+SALARY)
++++means+(PERSONNAME,+COMPANY,+SALARY)+IN+WorksFor
++++means+employee+PERSONNAME+works+at+COMPANY+for+$SALARY

/*+DRC+query+for+the+same+tuples+as+the+RA+query+above+*/
tuples+like+(PERSONNAME)+where
++++FOR+SOME+STREET+&+CITY+[Employee(PERSONNAME,+STREET,+CITY)]
AND+NOT+FOR+SOME+COMPANY+&+SALARY
++++++++[WorksFor(PERSONNAME,+COMPANY,+SALARY)+AND+COMPANY+=+'FBC']|5918520|TRC具有元组形式的量化名称。我们在名称上加点，以获得与其中的属性名称相关联的值。(类似于编程语言记录的字段。)我们对只有一个参数(一个元组)的语句使用简写：|5918521|Employee(T)
++++means+T+IN+Employee
++++means+employee+T.PERSONNAME+lives+on+T.STREET+in+T.CITY
Worksfor(T)
++++means+T+IN+Worksfor
++++means+employee+T.PERSONNAME+works+at+T.COMPANY+for+$T.SALARY

/*+TRC+query+for+the+same+tuples+as+the+RA+query+above+*/
tuples+equal+to+some+tuple+T+like+(PERSONNAME)+where
++++FOR+SOME+E+[Employee(E)+AND+E.PERSONNAME+=+T.PERSONNAME]
AND+NOT+FOR+SOME+W+[
++++++++WorksFor(W)
++++AND+W.COMPANY+=+'FBC'
++++AND+E.PERSONNAME+=+T.PERSONNAME
++++]|5918522|(讲授RA和RCs原件的一些变体。例如，一些通过顺序来识别参数，而另一些则通过名称来识别。有时会添加额外的功能。例如，在RC中允许函数调用就像在RA中允许某个关系常量加上操作符R将A重命名为N一样具有表现力。)|5918523|然而，RA运算符和RC运算符之间以及RA表达式和RC表达式之间存在对应关系：|5918524|如果：|5918525|·R+--保存元组，其中R(...)|5918526|·S+--保存元组，其中S(...)|5918527|然后：|5918528|·R+JOIN+S包含元组，其中R(...)和S(...)|5918529|·R+UNION+S包含元组，其中R(...)或S(...)|5918530|·R减去S保存元组，其中R(...)而不是S(...)|5918531|·要保留的R项目列包含要删除的某些列的元组，R(...)|5918532|·R限制条件保存元组，其中R(...)AND条件|5918533|RA表达式的值是满足相应RC表达式的元组。|5918534|如果我们希望在逐个运算符的基础上从RC表达式映射到RA表达式，那么我们需要扩展RA运算符:一个泛化UNION+&一个对应于NOT。这些运算符不是我们希望在实现中实际使用的运算符--在某种意义上，返回的关系值过大。但使用它们的每个RC表达式都可以机械地重新排列为只使用基本RA运算符的范式。|5918535|所以:+RA是过程性的，RCs是声明性的，这是一个神话。每个RA运算符具有对应的RC运算符，每个RC运算符具有(可能扩展的)对应的RA运算符，并且一个运算符的每个表达式具有另一个运算符的对应表达式(在基本和扩展意义上)。它们是同一事物的两个符号。任何一个的表达式都可以被认为是“过程性”的，通过将其作为解析或规范化来执行，而通过以其他方式执行来作为“声明性”。这个神话是试图捕捉RC表达式不像使用基本RA运算符的表达式那样逐个运算符的想法。但RC表达式确实使用基本运算符识别其非明显范式的RA表达式。它是逐个运算符的，就像包含扩展运算符的RA表达式一样。|5918536|(由于这些词的历史，这个神话可能会有所帮助。“现代代数”有运算符取值和赋值的表达式，可以计算。“微积分”又称分析--微分与积分--具有通过不可能计算的无限极限与求和来描述数值的表达式。我们以其他方式计算，通常只计算近似值。)|5918537|(另外，具有讽刺意味的是：“谓词演算”被认为是“声明性地”指定事物，而不考虑它们是如何计算或估计的。但是这种表达式的标准语义/含义是通过遍历表达式树的算法给出的。因此，它有一个明显的“程序性”解释。)|5918538|entityMap|0|LINK|mutability|MUTABLE|url|https://en.wikipedia.org/wiki/Set-builder_notation^0|0|6|0|0|0|0|0|0|C|K|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|25|8|@$9|26|A|27|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|28|8|@]|D|@]|E|$]]|$1|G|3|H|5|6|7|29|8|@]|D|@]|E|$]]|$1|I|3|J|5|K|7|2A|8|@]|D|@]|E|$L|M]]|$1|N|3|O|5|6|7|2B|8|@]|D|@]|E|$]]|$1|P|3|Q|5|K|7|2C|8|@]|D|@]|E|$L|M]]|$1|R|3|S|5|6|7|2D|8|@]|D|@$9|2E|A|2F|1|2G]]|E|$]]|$1|T|3|U|5|6|7|2H|8|@]|D|@]|E|$]]|$1|V|3|W|5|K|7|2I|8|@]|D|@]|E|$L|M]]|$1|X|3|Y|5|6|7|2J|8|@]|D|@]|E|$]]|$1|Z|3|10|5|K|7|2K|8|@]|D|@]|E|$L|M]]|$1|11|3|12|5|6|7|2L|8|@]|D|@]|E|$]]|$1|13|3|14|5|6|7|2M|8|@]|D|@]|E|$]]|$1|15|3|16|5|6|7|2N|8|@]|D|@]|E|$]]|$1|17|3|18|5|6|7|2O|8|@]|D|@]|E|$]]|$1|19|3|1A|5|6|7|2P|8|@]|D|@]|E|$]]|$1|1B|3|1C|5|6|7|2Q|8|@]|D|@]|E|$]]|$1|1D|3|1E|5|6|7|2R|8|@]|D|@]|E|$]]|$1|1F|3|1G|5|6|7|2S|8|@]|D|@]|E|$]]|$1|1H|3|1I|5|6|7|2T|8|@]|D|@]|E|$]]|$1|1J|3|1K|5|6|7|2U|8|@]|D|@]|E|$]]|$1|1L|3|1M|5|6|7|2V|8|@]|D|@]|E|$]]|$1|1N|3|1O|5|6|7|2W|8|@]|D|@]|E|$]]|$1|1P|3|1Q|5|6|7|2X|8|@]|D|@]|E|$]]|$1|1R|3|1S|5|6|7|2Y|8|@]|D|@]|E|$]]|$1|1T|3|1U|5|6|7|2Z|8|@]|D|@]|E|$]]|$1|1V|3|1W|5|6|7|30|8|@]|D|@]|E|$]]|$1|1X|3|-4|5|6|7|31|8|@]|D|@]|E|$]]]|1Y|$1Z|$5|20|21|22|E|$23|24]]]]

TL;DR: Queries calling RA (relational algebra) operators &amp; queries of the two relational calculi (RCs) TRC (tuple RC) &amp; DRC (domain RC) are different syntax for the same thing: a relation value or the property/condition that a relation value's tuples have to meet. As is SQL (a mix(up) of them). As is the predicate calculus, the language of precision in mathematics, logic, science (including computer science) &amp; engineering (including software engineering). And RA as procedural vs RCs as declarative is a myth.

<hr>

A relation holds the tuples that make some predicate--statement template parameterized by attributes--into a true proposition--statement.

<pre><code>/* tuples where employee PERSONNAME lives on STREET in CITY */
Employee
/* tuples where employee PERSONNAME works at COMPANY for $SALARY */
WorksFor
</code></pre>

A RA-style query expression involves attribute names, relation variable/constant names, relation literals (involving attribute names &amp; values) &amp; relation operators. The operators are JOIN, UNION, MINUS, PROJECT, RESTRICT, etc. It denotes the relation value that you get by evaluating the expression. But it is also requirements for the value to meet. 

<pre><code>/* RA query for tuples where
 FOR SOME STREET &amp; CITY [employee PERSONNAME lives on STREET in CITY]
AND NOT FOR SOME COMPANY &amp; SALARY
 [employee PERSONNAME works at COMPANY for $SALARY AND COMPANY = 'FBC']
*/
 PROJECT PERSONNAME (Employee)
MINUS PROJECT PERSONNAME (RESTRICT COMPANY = 'FBC' (WorksFor))
</code></pre>

A RC expression is <a href="https://en.wikipedia.org/wiki/Set-builder_notation" rel="nofollow noreferrer">set-builder notation</a> for a relation value. It involves a predicate with relation variable/constant names, attribute names &amp; values, predicate operators &amp; quantified names (logic variables). The operators are AND, OR, NOT, FOR SOME/ALL and =. It is usually seen as requirements for the value to meet. But it also denotes the relation value that you get by evaluating the expression or a certain equivalent one.

The DRC has quantified names that are attributes. We use a shorthand for statements with one parameter per attribute:

<pre><code>Employee(PERSONNAME, STREET, CITY)
 means (PERSONNAME, STREET, CITY) IN Employee
 means employee PERSONNAME lives on STREET in CITY
WorksFor(PERSONNAME, COMPANY, SALARY)
 means (PERSONNAME, COMPANY, SALARY) IN WorksFor
 means employee PERSONNAME works at COMPANY for $SALARY

/* DRC query for the same tuples as the RA query above */
tuples like (PERSONNAME) where
 FOR SOME STREET &amp; CITY [Employee(PERSONNAME, STREET, CITY)]
AND NOT FOR SOME COMPANY &amp; SALARY
 [WorksFor(PERSONNAME, COMPANY, SALARY) AND COMPANY = 'FBC']
</code></pre>

The TRC has quantified names that are tuples. We dot a name to get the value associated with an attribute name in it. (Like for a field of a programming language record.) We use a shorthand for statements with one parameter (a tuple):

<pre><code>Employee(T)
 means T IN Employee
 means employee T.PERSONNAME lives on T.STREET in T.CITY
Worksfor(T)
 means T IN Worksfor
 means employee T.PERSONNAME works at T.COMPANY for $T.SALARY

/* TRC query for the same tuples as the RA query above */
tuples equal to some tuple T like (PERSONNAME) where
 FOR SOME E [Employee(E) AND E.PERSONNAME = T.PERSONNAME]
AND NOT FOR SOME W [
 WorksFor(W)
 AND W.COMPANY = 'FBC'
 AND E.PERSONNAME = T.PERSONNAME
 ]
</code></pre>

(A few variants on the originals of the RA and RCs are taught. Eg some identify arguments by order and others by name. Sometimes extra capabilities are added. Eg allowing a function call in a RC is as expressive as allowing a certain relation constant plus operator R RENAME A TO N in a RA.) 

However, there is a correspondence between RA operators and RC operators &amp; between RA expressions and RC expressions:

If: 
 • R -- holds tuples where R(...) 
 • S -- holds tuples where S(...) 
then: 
 • R JOIN S holds tuples where R(...) AND S(...) 
 • R UNION S holds tuples where R(...) OR S(...) 
 • R MINUS S holds tuples where R(...) AND NOT S(...) 
 • R PROJECT columns to keep holds tuples where FOR SOME columns to drop, R(...) 
 • R RESTRICT condition holds tuples where R(...) AND condition 

A RA expression's value is the tuples that satisfy the corresponding RC expression.

If we want to map from a RC expression to an RA expression on an operator-by-operator basis then we need extended RA operators: one generalizing UNION &amp; one corresponding to NOT. Those aren't operators we would like to actually use in an implementation--the relations values returned are in a certain sense undesirably big. But every RC expression using them can be rearranged mechanically to a normal form that uses only basic RA operators.

So: RA as procedural vs RCs as declarative is a myth. Every RA operator has a corresponding RC operator, every RC operator has a (possibly extended) corresponding RA operator, and every expression of one has (in basic and extended senses) a corresponding expression of the other. They are two notations for the same things. An expression of either can be taken as "procedural" by executing it as parsed or normalized and as "declarative" by executing it otherwise. The myth is trying to capture the idea that a RC expression isn't operator-by-operator like an expression using basic RA operators. But a RC expression does identify its non-obvious normal form's RA expression using basic operators. And it is operator-by-operator like a RA expression including extended operators.

(The myth may be helped because of the history of the words. "Modern algebra" has expressions with operators taking &amp; giving values and can be calculated. "The calculus" aka analysis--differentiation &amp; integration--has expressions describing values via impossible-to-calculate infinite limits &amp; summations. We calculate in other ways, in general only calculating approximations.)

(Also, ironically: "The predicate calculus" is considered to specify things "declaratively" without regard to how they may be otherwise calculated or estimated. But the standard semantics/meaning of such an expression is given by following an algorithm that walks the expression tree. So it has an obvious "procedural" interpretation.)

blocks|key|4503013|text|关系代数与关系微积分的区别|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4503014|关系代数操作操纵某些关系，并以查询的形式提供一些表达式，其中关系演算是基于成对的expressions.|4503015|RA形成的查询，查询具有连接、并、交、除、差、投影、选择等算子，其中，当RC具有元组，面向域的expressions.|unordered-list-item|4503016|
|4503017|RA是过程性语言，其中，as是非过程性查询，RA和RC的system.|4503018|4503019|Expressive幂是等价的。这意味着任何可以用RA表示的查询都可以用RC中的公式表示。|4503020|4503021|任何KC公式都会在代数查询中转换。|4503022|4503023|在RA中的查询中有修改，这比RC更容易。|4503024|4503025|+RA形成了数学形式，没有specificjuer1语言RC也有数学形式，但有一种查询语言|4503026|4503027|RA查询比RC更容易操作和理解。|4503028|4503029|RC是WFFs，因为RA不形成任何公式。|4503030|4503031|RA是一个过程性的RA。这意味着我们已经按顺序编写了一些条件。|4503032|4503033|RC是非过程化的。在这里，我们以任意顺序编写条件。|4503034|4503035|示例：-|4503036|库示例：-|4503037|Book+is+a+relation+it+have+a+following+attributes.

++++++1.+Book+Name
++++++2.+Accession+Number
++++++3.+Year+of+publication|code-block|syntax|javascript|4503038|问题：-|4503039|+Find+out+the+all+book+names+published+in+the+year+2000|4503040|关系代数：|4503041|+++-------------------------------------------------------
+++%7C+++++++++++++++++++++++(σ++++++++++++(book)+)++++++++%7C
+++%7C+++++++¶+++++++++++++++++(yr_pub=2000)+++++++++++++++%7C
+++%7C++++++++(Book+name)++++++++++++++++++++++++++++++++++%7C
++++------------------------------------------------------|4503042|关系演算：|4503043|++++S+=+{+t+%7C+∃+u+∈++book+(t[book+name]+=+u[book+name])+∧+(u[yr_pub]+=+2000+)+}|4503044|在这个关系演算中，我们可以将条件写在任何地方，如下所示。|4503045|++++S+=+{+t+%7C+∃+u+∈++book++(u[yr_pub]+=+2000+)+∧+(t[book+name]+=+u[book+name])++}|4503046|但在关系代数中，我们必须首先找到出版年份为2000的元组是什么，然后只需提取图书名称列。|4503047|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|22|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|23|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|24|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|25|8|@]|9|@]|A|$]]|$1|I|3|J|5|F|7|26|8|@]|9|@]|A|$]]|$1|K|3|H|5|6|7|27|8|@]|9|@]|A|$]]|$1|L|3|M|5|F|7|28|8|@]|9|@]|A|$]]|$1|N|3|H|5|6|7|29|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|2A|8|@]|9|@]|A|$]]|$1|Q|3|H|5|6|7|2B|8|@]|9|@]|A|$]]|$1|R|3|S|5|F|7|2C|8|@]|9|@]|A|$]]|$1|T|3|H|5|6|7|2D|8|@]|9|@]|A|$]]|$1|U|3|V|5|F|7|2E|8|@]|9|@]|A|$]]|$1|W|3|H|5|6|7|2F|8|@]|9|@]|A|$]]|$1|X|3|Y|5|F|7|2G|8|@]|9|@]|A|$]]|$1|Z|3|H|5|6|7|2H|8|@]|9|@]|A|$]]|$1|10|3|11|5|F|7|2I|8|@]|9|@]|A|$]]|$1|12|3|H|5|6|7|2J|8|@]|9|@]|A|$]]|$1|13|3|14|5|F|7|2K|8|@]|9|@]|A|$]]|$1|15|3|H|5|6|7|2L|8|@]|9|@]|A|$]]|$1|16|3|17|5|F|7|2M|8|@]|9|@]|A|$]]|$1|18|3|-4|5|6|7|2N|8|@]|9|@]|A|$]]|$1|19|3|1A|5|6|7|2O|8|@]|9|@]|A|$]]|$1|1B|3|1C|5|6|7|2P|8|@]|9|@]|A|$]]|$1|1D|3|1E|5|1F|7|2Q|8|@]|9|@]|A|$1G|1H]]|$1|1I|3|1J|5|6|7|2R|8|@]|9|@]|A|$]]|$1|1K|3|1L|5|1F|7|2S|8|@]|9|@]|A|$1G|1H]]|$1|1M|3|1N|5|6|7|2T|8|@]|9|@]|A|$]]|$1|1O|3|1P|5|1F|7|2U|8|@]|9|@]|A|$1G|1H]]|$1|1Q|3|1R|5|6|7|2V|8|@]|9|@]|A|$]]|$1|1S|3|1T|5|1F|7|2W|8|@]|9|@]|A|$1G|1H]]|$1|1U|3|1V|5|6|7|2X|8|@]|9|@]|A|$]]|$1|1W|3|1X|5|1F|7|2Y|8|@]|9|@]|A|$1G|1H]]|$1|1Y|3|1Z|5|6|7|2Z|8|@]|9|@]|A|$]]|$1|20|3|-4|5|6|7|30|8|@]|9|@]|A|$]]]|21|$]]

Difference between the Relational algebra and the Relational Calculus

<ol>
<li>Relational algebra operations manipulate some relations and provide some expression in the form of queries where as relational calculus are formed queries on the basis of pairs of expressions.</li>
<li>RA have operator like join, union, intersection, division, difference, projection, selection etc. where as RC has tuples and domain oriented expressions.</li>
<li>RA is procedural language where as RC is non procedural query system.</li>
<li>Expressive power of RA and RC are equivalent. This means any query that could be expressed in RA could be expressed by formula in RC.</li>
<li>Any KC formula is translated in Algebric query.</li>
<li>There is modification which is easy in queries in RA than the RC.</li>
<li>RA formed the mathematical form and have no specificjuer1 language RC also has mathematical form but has one query language QUEL.</li>
<li>Relational algebra is easy to manipulate and understand than RC.</li>
<li>RA queries are more powerful than the RC.</li>
<li>RC are formed WFFs where as RA does not form any formula.</li>
<li>RA is a procedural. That means we have write some conditions in order.</li>
<li>RC is a Non procedural. In here we have write the conditions in any order.</li>
</ol>

Example:-

Library Example:-

<pre><code>Book is a relation it have a following attributes.

 1. Book Name
 2. Accession Number
 3. Year of publication
</code></pre>

Problem:-

<pre><code> Find out the all book names published in the year 2000
</code></pre>

Relational Algebra:-

<pre><code> -------------------------------------------------------
 | (σ (book) ) |
 | ¶ (yr_pub=2000) |
 | (Book name) |
 ------------------------------------------------------
</code></pre>

Relational calculus:-

<pre><code> S = { t | ∃ u ∈ book (t[book name] = u[book name]) ∧ (u[yr_pub] = 2000 ) }
</code></pre>

In this relational calculus we can write the condition in any where like the below.

<pre><code> S = { t | ∃ u ∈ book (u[yr_pub] = 2000 ) ∧ (t[book name] = u[book name]) }
</code></pre>

But in relational algebra, we have to find first what are the tuples have the year of publication is 2000, then only we have to extract the book name column.

What is the exact difference between relational algebra and relational calculus. At most of the reference, it will be 

<code>Relational algebra is procedural and calculus is non procedural</code>. 

So, what is these stands for. However, we can solve all the problems using relational
algebra. Then why we would use relational calculus. Except definition, Explanation with example is much appreciated.

Difference between Relational Algebra and Relational calculus

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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关系代数和关系微积分的确切区别是什么？在大多数引用中，它将是Relational algebra is procedural and calculus is non procedural。那么，这些代表的是什么。但是，我们可以使用关系代数来解决所有问题。那么为什么我们要使用关系演算。除了定义，用例子来解释是非常有价值的...

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