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key is nothing but a attribute and attribute is the aspect of a member in an entity
entity is represented by set of attributes.
primary key is the one which is selected by the database designer to identify a entity in a entity set
super key is one or more attributes which is used to identify the entity in an entity set uniquely
candidate key minimal number of super keys... in some context super key and secondary key are equal.
foreign key is the relational constraint between tables or entities
A secondary key is made on a field that you would like to be indexed for faster searches!
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Wiki User
∙ 13y ago
Wiki User
∙ 11y agoEach table in a database should have a primary key. The primary key is the main way to identify each record in a table. It is usually specified as a field, or a combination of fields, that will be unique for every record. For example, in a list of clients, the primary key may be the combination of the first and last name (not a good choice, since these may repeat), the client code that is printed on invoiced, etc. (better, since each client can be assigned a unique code), or - even better - a sequential number assigned automatically by the DBMS to every client.
The primary key is used in other tables as a foreign key. For example, the client code may be used in invoices to identify to which client the invoice corresponds.
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What are the two coils in a transformer?
primary and secondary coilsAnswerPrimary and secondary windings.
Is the transformer's iron core called the primary?
No. the primary winding is called the primary; the secondary winding is called the secondary. These are both wrapped around the iron core of the transformer. The core helps magnetically link the primary and secondary, which causes the transformation of voltage and current from primary to secondary.
Why transformar primary refers to secondary?
All transformers contain both primary and secondary coils. The primary will refer to the secondary when the voltage is to high. As voltage increases, it passes down the power to the secondary for efficient distribution of power.
When can be current in a primary coil induce a current in a secondary coil?
Secondary current = Primary current *(Number of secondary turns /Number of primary) turnsAnswerA current isn't 'induced' into the secondary winding of a transformer. It's a voltage that is induced into the secondary winding.Provided the secondary winding is connected to a load, the secondary voltage then supplies a secondary current which is determined from (Is = Vs/Rload). The primary current then depends upon the value of the secondary current and the turns ratio.
What is the current in the secondary coil if current in primary is 5.0A?
It depends on the turns ratio between the primary and the secondary. If the ratio were 10:1, a step-down transformer, for instance, the current in the secondary would be about 50A. If it were 1:10, a step-up transformer, however, the current in the secondary would be about 0.5A.AnswerThe primary current doesn't determine the secondary current. The secondary current is entirely-dependent on the secondary voltage and the impedance of the load. It is this secondary current that the determines the primary current. So you should be asking, "What value of secondary current would result in a primary current of 5.0 A?"
What is secondary indexes in dbms?
secondary index is a key which is created other than primary key, to speed up processing.
What ensures the value of the foreign key matches another tables primary key?
It is the DBMS that ensures the value of the foreign key matches another table's primary key when referential integrity constraints are enabled within the DBMS
What is stored as primary key in a second table?
a secondary key
What is the difference between a Primary Key and a Secondary Key?
A Primary Key is a unique identifier for each record in a database table and is used to enforce entity integrity. A Secondary Key is a non-unique index that is used for querying and organizing data efficiently but does not have the constraint of uniqueness.
What is the difference between primary key and secondary key in database?
A primary key is a unique identifier for each record in a database table and is used to ensure data integrity and enforce entity integrity. A secondary key, also known as a candidate key, is an alternate unique key that can be used to identify records, but is not designated as the primary key.
Primary and secondary key in c and c plus plus?
There are no "primary and secondary keys" in c and c plus plus.
What is the difference between primary key and secondary key?
There is two difference between them. 1. The not null constraint is by default added to primary key, it means, primary key attribute cannot accept null values, whereas, the attribute declared as unique can accept null values. It is the major difference between the two. 2. Secondly, we can have only one primary key in a relation, whereas, multiple attributes can be declared unique at the same time.
What is the prime attribute in DBMS?
prime attributes are the attributes of a candidate key which will give uniqueness. a candidate key is (the subset of superkey) which gives uniqueness. Super key is the maximum set of attributes that can provide uniqueness example ABCDE is a super key AB CD DE are the candidate keys s.t. AB is the primary key. CD and DE are the secondary/alternate keys.
What is candidate key in dbms?
more than one primary key to identify the record uniquely is called candidate key.
What is weak entity sets in dbms?
An entity set may not have sufficient attributes to form a primary key is called weak entity set. One with primary key is called strong entity set.
What questions may be asked in IGNOU's BCA project viva?
DFD SDLC primary key unique key etc......... study DBMS very well and ur project
What is a secondary key in relational databases?
A secondary key is a field that is identified as being suitable for indexing the data such as a surname, It is used to sort the data in a different order to the primary key, A table can have many secondary keys in fact every field could be a secondary key. Hope this helps !
