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To trim a string in jQuery, use the trim() method. It removes the spaces from starting and end of the string.The sample string I am using has spaces −var myStr = " Hello World ";Use the trim() method, jQuery.trim(myStr);The following is an example to trim a string in jQuery −ExampleLive Demo $(document).ready(function(){ $("#button1").click(function(){ var myStr = " Hello World "; myStr = jQuery.trim(myStr); alert(myStr); }); }); Trim
What is 4NF?The 4NF comes after 1NF, 2NF, 3NF, and Boyce-Codd Normal Form. It was introduced by Ronald Fagin in 1977.To be in 4NF, a relation should be in Bouce-Codd Normal Form and may not contain more than one multi-valued attribute.ExampleLet us see an example −Movie_NameShooting_LocationListingMovieOneUKComedyMovieOneUKThrillerMovieTwoAustraliaActionMovieTwoAustraliaCrimeMovieThreeIndiaDramaThe above is not in 4NF, sinceMore than one movie can have the same listingMany shooting locations can have the same movieLet us convert the above table in 4NF −Movie_NameShooting_LocationMovieOneUKMovieOneUKMovieTwoAustraliaMovieTwoAustraliaMovieThreeIndiaMovie_NameListingMovieOneComedyMovieOneThrillerMovieTwoActionMovieTwoCrimeMovieThreeDramaNow the violation is removed and the tables are in 4NF.
A Foreign Key creates a link between tables. It references the primary key in another table and links it.For example, the DeptID in the Employee table is a foreign key −EmpIDEmpNameEmpAgeDeptIDDeptIDDeptNameDeptZoneThe DeptID in the Department table is a Primary Key in the Department Table.The DeptID in the Employee table is a Foreign Key in the Employee Table.The below figure represents the same −Above, you can see our two tables. The Foreign Key of the Employee table is the Primary Key of the Department table.
Each table has only a single primary key. Each relation may have one or more candidate key. One of these candidate key is called Primary Key. Each candidate key qualifies for Primary Key. Therefore candidates for Primary Key is called Candidate Key.Candidate key can be a single column or combination of more than one column. A minimal super key is called a candidate key.ExampleEmployeeID and EmployeeEmail, both can be a Primary key; therefore both are candidate keys. Select any of the as Primary Key for your table, since a table can have only a single Primary Key.Let us see another example ... Read More
A relation is in DKNF when insertion or delete anomalies are not present in the database. Domain-Key Normal Form is the highest form of Normalization. The reason is that the insertion and updation anomalies are removed. The constraints are verified by the domain and key constraints.A table is in Domain-Key normal form only if it is in 4NF, 3NF and other normal forms. It is based on constraints −Domain ConstraintValues of an attribute had some set of values, for example, EmployeeID should be four digits long −EmpIDEmpNameEmpAge0921Tom330922Jack31Key ConstraintAn attribute or its combination is a candidate keyGeneral ConstraintPredicate on the set ... Read More
What is a Secondary KeySecondary Key is the key that has not been selected to be the primary key. However, it is considered a candidate key for the primary key.Therefore, a candidate key not selected as a primary key is called secondary key. Candidate key is an attribute or set of attributes that you can consider as a Primary key.Note: Secondary Key is not a Foreign Key.ExampleLet us see an example −Student_IDStudent_EnrollStudent_NameStudent_AgeStudent_Email0969122717Manish25aaa@gmail.com0559122655Manan23abc@gmail.com0679122699Shreyas28pqr@gmail.comAbove, Student_ID, Student_Enroll and Student_Email are the candidate keys. They are considered candidate keys since they can uniquely identify the student record. Select any one of the candidate key as ... Read More
What is Transitive DependencyWhen an indirect relationship causes functional dependency it is called Transitive Dependency.If P -> Q and Q -> R is true, then P-> R is a transitive dependency.To achieve 3NF, eliminate the Transitive Dependency.ExampleMovie_IDListing_IDListing_TypeDVD_Price ($)M08L09Crime180M03L05Drama250M05L09Crime180The above table is not in 3NF because it has a transitive functional dependency −Movie_ID -> Listing_IDListing_ID -> Listing_TypeTherefore, the following has transitive functional dependency.Movie_ID -> Listing_TypeThe above states the relation violates the 3rd Normal Form (3NF).To remove the violation, you need to split the tables and remove the transitive functional dependency.Movie_IDListing_IDDVD_Price ($)M08L09180M03L05250M05L09180Listing_IDListing_TypeL09CrimeL05DramaL09CrimeNow the above relation is in Third Normal Form (3NF) ... Read More
For Entity Integrity Rule, each table has a Primary Key.Primary Key cannot have NULL value.Student_IDStudent_AwardsStudent_AwardsAbove, you can see our primary key is Student_ID. We cannot consider Student_Awards as the primary key since not every student would have received the award.Let us see another example −Employee_IDEmployee_NameEmployee_AgeEmployee_LocationIn the above table, the Primary Key is Employee_IDLet us now summarize the Entity Integrity Rule −Make sure that each tuple in a table is unique.Every table mush has a primary key, for example, Student_ID for a Student table.Every entity is unique.The relations Primary Key must have unique values for each row.Primary Key cannot have NULL ... Read More
defaultThis came to handle function parameters with ease. Easily set Default parameters to allow initializing formal parameters with default values. This is possible only if no value or undefined is passed. Let’s see an exampleExampleLive Demo // default is set to 1 function inc(val1, inc = 1) { return val1 + inc; } document.write(inc(10, 10)); document.write(""); document.write(inc(10)); restES6 ... Read More
The jQuery.extend() method is used to merge contents of two or more objects together. The object is merged into the first object. You can try to run the following code to learn how to use extend() method −ExampleLive Demo $(document).ready(function() { $("#button1").click(function() { var obj1 = { maths: 60, history: {pages: 150,price: 400,lessons: 30}, science: 120 }; var obj2 = { history: { price: 150, lessons: 24 }, economics: 250 }; $.extend(true, obj1, obj2); $("#demo").append(JSON.stringify(obj1)); }); }); Result