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Database Articles
Page 296 of 547
Identifying Entity Relationships in DBMS
Identifying entity relationships in DBMS is used to identify a relationship between strong and weak entity.Before beginning, let us take an example of Professor entity, which is our Strong Entity, with Professor_ID as a Primary Key −Professor_IDProfessor_NameProfessor_CityProfessor_SalaryThe weak entity is Professor_Dependents entity:NameDOBRelationNow, let us continue, Weak EntityWeak Entity is dependent on Strong Entity and does not have a primary key. Weak Entity has a partial key. It is represented as double rectangle −Strong EntityOther entities are dependent on Strong Entity and it has a key attribute i.e. a primary key and represented as a single rectangle.Identifying RelationshipsIt links the strong and weak entity ...
Read MoreEvolution of Data Models
Managing data was the key and was essential. Therefore, data model originated to solve the file system issues. Here are the Data Models in DBMS −Hierarchical ModelIn Hierarchical Model, a hierarchical relation is formed by collection of relations and forms a tree-like structure.The relationship can be defined in the form of parent child type.One of the first and most popular Hierarchical Model is Information Management System (IMS), developed by IBM.ExampleThe hierarchy shows an Employee can be an Intern, on Contract or Full- Time. Sub-levels show that Full-Time Employee can be hired as a Writer, Senior Writer or Editor:AdvantagesThe design of ...
Read MoreEverything is stored in database in SAP system
Note that it is easy to store data in form of SAP database tables as compared to files. You can also access files in SAP system but they are available on file system of SAP Application server and not easy to use with.With use of ABAP, you can easily raise queries against database tables and it is safe to run queries to get data. SAP has various tools that allow you to work with table entries and also to manage entire landscape easily.What databases are supported by SAP?PartnerVendorMicrosoft SQL Serverwww.microsoft.comMySQL MaxDBwww.mysql.comIBM DB2 (various versions)www.ibm.comOraclewww.oracle.comAlso SAP has its own in-memory computing ...
Read MoreDifference between Simple and Complex View in SQL
Before discussing on Simple and complex, first we should know what is View. A View is the logical virtual table created from one or more tables which can be primarily used to fetch the columns from one or more different tables at a time. On the basis of tables involved in the view we can distinguish between Simple and Complex View in SQL.Following are the important differences between Simple and Complex View.Sr. No.KeySimple ViewComplex View1DefinitionSimple View in SQL is the view created by involving only single table. In other words we can say that there is only one base table ...
Read MoreWhat is the difference between BLOB and CLOB datatypes?
Blob and Clob together are known as LOB(Large Object Type). The following are the major differences between Blob and Clob data types.BlobClobThe full form of Blob is a Binary Large Object.The full form of Clob is Character Large Object.This is used to store large binary data.This is used to store large textual data.This stores values in the form of binary streams.This stores values in the form of character streams.Using this you can stores files like videos, images, gifs, and audio files.Using this you can store files like text files, PDF documents, word documents etc.MySQL supports this with the following datatypes:TINYBLOBBLOBMEDIUMBLOBLONGBLOBMySQL ...
Read MoreCount no. of characters and words in a string in PL/SQL
We are given a string of any length and the task is to calculate the count of characters and words in a string using PL/SQL.PL/SQL is a combination of SQL along with the procedural features of programming languages.It was developed by Oracle Corporation in the early 90's to enhance the capabilities of SQL. PL/SQL is one of three key programming languages embedded in the Oracle Database, along with SQL itself and Java.In PL/SQL block, we have DECLARE block which is used to declare the variables used in programming and we have BEGIN block where we write the logic for the ...
Read MoreConvert distance from km to meters and centimeters in PL/SQL
The task is to convert the distance from kilometers to meters and centimeters in PL/SQL.PL/SQL is the extension of SQL which combines the Data manipulation of SQL with the working of procedural language.According to the problem we should have distance in kilometers whose value we have to convert in meters and centimeters.As per the conversion rule −1km = 1000 meters1km = 100000 centimetersAccording to this conversion rule we want the distance to be converted by a logic in PL/SQL.ExampleInput: kilometer = 10 Output: meter = 10000 Centimeter = 1000000 Input: kilometer = 9 Output: meter = 9000 Centimeter ...
Read MoreMySQL query to remove numbers after hyphen in a VARCHAR string with numbers
For this, use SUBSTRING_INDEX(). Let us first create a table −mysql> create table DemoTable2040 -> ( -> StudentCode varchar(20) -> ); Query OK, 0 rows affected (0.85 sec)Insert some records in the table using insert command −mysql> insert into DemoTable2040 values('John-232'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable2040 values('Carol-901'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable2040 values('David-987'); Query OK, 1 row affected (0.21 sec)Display all records from the table using select statement −mysql> select *from DemoTable2040;This will produce the following output −+-------------+ | StudentCode | +-------------+ | ...
Read MoreDisplaying only a list of records in ASC order with MySQL
To display a list of records in a specific order, you need to set conditions and use ORDER BY. For this, use ORDER BY CASE statement. Let us first create a table −mysql> create table DemoTable2039 -> ( -> Name varchar(20) -> ); Query OK, 0 rows affected (0.62 sec)Insert some records in the table using insert command −mysql> insert into DemoTable2039 values('John Doe'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable2039 values('John Smith'); Query OK, 1 row affected (0.08 sec) mysql> insert into DemoTable2039 values('Chris Brown'); Query OK, 1 row affected ...
Read MoreMySQL query to return TRUE for rows having positive value?
To return TRUE for positive values and FALSE for negative, use MySQL IF(). Let us first create a table −mysql> create table DemoTable2038 -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Value int -> ); Query OK, 0 rows affected (0.87 sec)Insert some records in the table using insert command −mysql> insert into DemoTable2038(Value) values(57); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable2038(Value) values(-100);; Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable2038(Value) values(-78); Query OK, 1 row affected (0.42 sec) mysql> insert into DemoTable2038(Value) ...
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