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Database Articles
Page 283 of 547
How can we store a value in user-defined variable?
We can store a value in a user-defined variable in a statement and then refer to it afterward in other statements. Followings are the ways to store a value in user-defined variable −With SET statementwe can store a user-defined variable by issuing a SET statement as follows −SyntaxSET @var_name = expr[, @var_name = expr]…In this @var_name is the variable name which consists of alphanumeric characters from current character set. We can use either = or := assignment operator with SET statement.For example following queries can store the user variables with SET statement −mysql> SET @value = 500; Query OK, 0 ...
Read MoreWhat happens with the output of MySQL EXPORT_SET() function if I will skip the value of the fifth argument i.e. a number of bits?
Actually, the default value of the fifth argument i.e. number of bits is 64, hence if we will not specify any value on fifth argument them MySQL will check the bits up to 64 bits and produce the result. It can be understood from the following example −Examplemysql> SELECT EXPORT_SET(5, 'Y', 'N', ' ')\G *************************** 1. row *************************** EXPORT_SET(5, 'Y', 'N', ' '): Y N Y N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N ...
Read MoreHow MySQL FIELD() and ELT() functions are complements of each other?
On the basis of the working of both the functions, we can say that both are the complement of each other. Actually, as we know that FIELD() function, on providing a string as an argument, returns the index number of the string from string list and ELT() function, on providing index number as an argument, returns the string from string list. In the following example, we have applied both the functions on the same string, it would demonstrate the concept −Examplemysql> SELECT ELT(4, 'Ram', 'is', 'good', 'boy')As Result; +--------+ | Result | +--------+ | boy | +--------+ ...
Read MoreWhat would be the output of MySQL ELT() function if the index number, provided as an argument, is not an integer?
As we know the 1st argument of ELT() function must be an integer value but when we provide index number which is not an integer the MySQL ELT() function returns NULL with a warning.Examplemysql> select ELT('one','Ram,is,good,boy')As Result; +--------+ | Result | +--------+ | NULL | +--------+ 1 row in set, 1 warning (0.00 sec) mysql> Show Warnings; +---------+------+------------------------------------------+ | Level | Code | Message | +---------+------+------------------------------------------+ | Warning | 1292 | Truncated incorrect INTEGER value: 'one' | +---------+------+------------------------------------------+ 1 row in set (0.00 sec)
Read MoreCursors in Oracle DBMS
When a SQL statement is executed in Oracle, the temporary context area is created. This area contains all the relevant information relating to the statement and its execution. The cursor is a pointer to this context area and allows the PL/SQL program to control this area.There are two types of Cursors.Implicit CursorsExplicit CursorsLet us begin with Implicit Cursors −Implicit CursorsWhenever an SQL statement is executed, the implicit cursors are automatically created. This happens if there is no explicit cursor for the particular statement. Implicit cursors cannot be controlled by the programmers.There are many different attributes for Implicit Cursors. Some of ...
Read MoreIn MySQL, how FIELD() function is different from FIND_IN_SET() function?
As we know, both the functions are used to search a string from the arguments provided in them but there are some significant differences between them as follows −FIND_IN_SET() − function uses the string list that is itself a string containing the substring separated by commas. Whereas, FIELD() function contains list of different strings among which it will find the index number of the string, if present, which is to be searched.FIND_IN_SET() − function returns NULL if any of the argument i.e. either search string or string list is NULL. In contrast, FIELD() function do not returns NULL but returns ...
Read MoreDDBMS Components
The contents of a distributed database are spread across multiple locations. That means the contents may be stored in different systems that are located in the same place or geographically far away. However, the database still appears uniform to the users i.e the fact that the database is stored at multiple locations is transparent to the users.The different components of a distributed database are −Let us now discuss them one by one −UsersThere are many users who use the distributed database. For them, the fact that the database is spread across multiple locations is transparent and they perceive the database ...
Read MoreWhat MySQL ELT() function returns if the index number, provided as an argument, is higher than the number of strings?
MySQL ELT() function returns NULL as output if the index number provided as argument is higher than the number of strings. Following is an example to make it clearer −Examplemysql> Select ELT(6,'Ram','is','a','good','boy')As Result; +--------+ | Result | +--------+ | NULL | +--------+ 1 row in set (0.00 sec)As we can see that index number is 6 and the list of strings is having only 5 strings. Hence MySQL returns NULL.
Read MoreWhen MySQL FIND_IN_SET() function returns NULL as output?
FIND_IN_SET() function returns NULL as output if any of the argument i.e. either search string or string list, is NULL. Of course, It will also return NULL if both of the arguments are NULL.Examplemysql> Select FIND_IN_SET(NULL,'Ram is a good boy') AS Result; +--------+ | Result | +--------+ | NULL | +--------+ 1 row in set (0.00 sec) mysql> SELECT FIND_IN_SET('RAM',NULL)AS RESULT; +--------+ | RESULT | +--------+ | NULL | +--------+ 1 row in set (0.00 sec) mysql> SELECT FIND_IN_SET(NULL,NULL); +------------------------+ | FIND_IN_SET(NULL,NULL) | +------------------------+ | NULL | +------------------------+ 1 row in set (0.00 sec)
Read MoreOverview of Packages in Oracle
Packages are SQL procedures, functions, variables, statements etc. that are grouped into a single unit. Many different applications can share the contents of a package, as it is stored in the database.Parts of a PackageThe following are the parts of a package in Oracle −Package SpecificationThe package specifications contains information about all the procedures, functions, variables, constants etc. stored inside it. It has the declaration of all the components but not the code.All the objects that are in the specification are known as public objects. If there is any object that is not available in the specification but is coded ...
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