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Articles by karthikeya Boyini
Page 130 of 143
MySQL add “prefix” to every column?
To create a view only if it does not already exist, you can use the following syntax −CREATE OR REPLACE VIEW yourViewName AS SELECT *FROM yourTableName;To understand the above syntax, let us create a table. The query to create a table is as follows −mysql> create table createViewDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Name varchar(20) -> ); Query OK, 0 rows affected (0.58 sec)Insert some records in the table using insert command. The query is as follows −mysql> insert into createViewDemo(Name) values('John'); Query OK, 1 row affected (0.22 sec) mysql> insert into ...
Read MoreHow to check if a table exists in MySQL and create if it does not already exist?
If you try to create a table and the table name already exist then MySQL will give a warning message. Let us verify the concept.Here, we are creating a table that already exist −mysql> CREATE TABLE IF NOT EXISTS DemoTable ( CustomerId int, CustomerName varchar(30), CustomerAge int ); Query OK, 0 rows affected, 1 warning (0.05 sec)The table name DemoTable is already present. Let us check the warning message.Following is the query −mysql> show warnings;This will produce the following output i.e. the warning message −+-------+------+------------------------------------+ | Level | Code | Message ...
Read MoreCommand to check read/write ratio in MySQL?
To check the read/write ratio, you need to use SHOW STATUS command. This will give all the ratios.Case 1 − The syntax is as follows to get the read/write ratio −SHOW STATUS LIKE ‘Com_%’;Case 2 − If you want the insert, update, select and delete ratio, use the below syntax −SHOW GLOBAL STATUS WHERE Variable_name = 'Com_insert' OR Variable_name = 'Com_select' OR Variable_name = 'Com_Update' OR Variable_name = 'Com_delete';Here is no need to do any changes in the above syntax. The query is as follows −mysql> SHOW GLOBAL STATUS WHERE Variable_name = 'Com_insert' OR Variable_name = 'Com_select' OR -> ...
Read MoreJavaTuples addAtX() method for Triplet class
The addAtX() method is used to add a value to the Triplet Tuple. The index can be set here with the X i.e. the place where the value gets added.Let us first see what we need to work with JavaTuples. To work with Triplet class in JavaTuples, you need to import the following package −import org.javatuples.Triplet;Here, we have used Quartet class also, therefore import the following −import org.javatuples.Quartet;Note − Steps to download and run JavaTuples program. If you are using Eclipse IDE to run Triplet Class in JavaTuples, then Right Click Project ->Properties ->Java Build Path ->Add External Jars and ...
Read MoreHow to avoid inserting duplicate rows in MySQL?
To avoid inserting duplicate rows in MySQL, you can use UNIQUE(). The syntax is as follows −ALTER TABLE yourTableName ADD UNIQUE(yourColumnName1, yourColumnName2, ...N);To understand the above syntax, let us create a table. The query to create a table is as follows −mysql> create table avoidInsertingDuplicateRows -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> FirstValue int, -> SecondValue int -> ); Query OK, 0 rows affected (0.53 sec)Now check the description of table using desc command. The query is as follows −mysql> desc avoidInsertingDuplicateRows;Sample The following is The output −+-------------+---------+------+-----+---------+----------------+ | Field ...
Read MoreHow to set result of a java expression in a property in JSP?
The tag is JSTL-friendly version of the setProperty action. The tag is helpful because it evaluates an expression and uses the results to set a value of a JavaBean or a java.util.Map object.AttributeThe tag has the following attributes −AttributeDescriptionRequiredDefaultValueInformation to saveNobodytargetName of the variable whose property should be modifiedNoNonepropertyProperty to modifyNoNonevarName of the variable to store informationNoNonescopeScope of variable to store informationNoPageIf target is specified, property must also be specified.Example Tag Example The above code will generate the following result −4000
Read MoreResolve ERROR 1111 (HY000): Invalid use of group function in MySQL? How to correctly use aggregate function with where clause?
To correctly use aggregate function with where clause in MySQL, the following is the syntax −select *from yourTableName where yourColumnName > (select AVG(yourColumnName) from yourTableName);To understand the above concept, let us create a table. The query to create a table is as follows −mysql> create table EmployeeInformation -> ( -> EmployeeId int, -> EmployeeName varchar(20), -> EmployeeSalary int, -> EmployeeDateOfBirth datetime -> ); Query OK, 0 rows affected (1.08 sec)Now you can insert some records in the table using insert command. The query is as follows −mysql> insert into EmployeeInformation values(101, 'John', 5510, '1995-01-21'); ...
Read MoreHow to apply choose tag in JSP?
The works like a Java switch statement in that it lets you choose between a number of alternatives. Where the switch statement has case statements, the tag has tags. Just as a switch statement has the default clause to specify a default action, has as the default clause.AttributeThe tag does not have any attribute.The tag has one attributes which is listed below.The tag does not have any attribute.The tag has the following attributes −AttributeDescriptionRequiredDefaulttestCondition to evaluateYesNoneExample Tag Example ...
Read MoreWhat are advantages of using JSP?
Following table lists out the other advantages of using JSP over other technologies −vs. Active Server Pages (ASP)The advantages of JSP are twofold. First, the dynamic part is written in Java, not Visual Basic or other MS specific language, so it is more powerful and easier to use. Second, it is portable to other operating systems and non-Microsoft Web servers.vs. Pure ServletsIt is more convenient to write (and to modify!) regular HTML than to have plenty of println statements that generate the HTML.vs. Server-Side Includes (SSI)SSI is really only intended for simple inclusions, not for "real" programs that use form ...
Read MoreSearching BETWEEN dates stored as varchar in MySQL?
You can search between dates stored as varchar using STR_TO_DATE(). The syntax is as follows −select *from yourTableName where STR_TO_DATE(LEFT(yourColumnName, LOCATE('', yourColumnName)), '%m/%d/%Y') BETWEEN 'yourDateValue1' AND 'yourDateValue2’;To understand the above syntax, let us create a table. The query to create a table is as follows −mysql> create table SearchDateAsVarchar -> ( -> Id int NOT NULL AUTO_INCREMENT, -> ShippingDate varchar(100), -> PRIMARY KEY(Id) -> ); Query OK, 0 rows affected (0.99 sec)Insert some records in the table using INSERT command. The query is as follows −mysql> insert into SearchDateAsVarchar(ShippingDate) values('6/28/2011 9:58 AM'); Query OK, 1 ...
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