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Articles by George John
Page 62 of 79
Resolve Unknown database in JDBC error with Java-MySQL?\\n
This type of error occurs if you select any database that does not exist in MySQL. Let us first display the error of unknown database in JDBC.The Java code is as follows. Here, we have set the database as ‘onlinebookstore’, which does not exist:import java.sql.Connection; import java.sql.DriverManager; public class UnknownDatabaseDemo { public static void main(String[] args) { String JdbcURL = "jdbc:mysql://localhost:3306/onlinebookstore?useSSL=false"; String Username = "root"; String password = "123456"; Connection con = null; try { con = DriverManager.getConnection(JdbcURL, Username, password); ...
Read MoreDifference between count(*) and count(columnName) in MySQL?
The count(*) returns all rows whether column contains null value or not while count(columnName) returns the number of rows except null rows.Let us first create a table.Following is the querymysql> create table ifNotNullDemo -> ( -> Name varchar(20) -> ); Query OK, 0 rows affected (0.54 sec)Following is the query to insert some records in the table using insert command:mysql> insert into ifNotNullDemo values('Chris'); Query OK, 1 row affected (0.15 sec) mysql> insert into ifNotNullDemo values(''); Query OK, 1 row affected (0.13 sec) mysql> insert into ifNotNullDemo values('Robert'); Query OK, 1 row affected (0.24 sec) ...
Read MoreCan we order a MySQL result with mathematical operations?\\n
Yes, we can order with mathematical operations using ORDER BY clause. Let us first create a table:mysql> create table orderByMathCalculation -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Quantity int, -> Price int -> ); Query OK, 0 rows affected (0.57 sec)Following is the query to insert some records in the table using insert command:mysql> insert into orderByMathCalculation(Quantity, Price) values(10, 50); Query OK, 1 row affected (0.21 sec) mysql> insert into orderByMathCalculation(Quantity, Price) values(20, 40); Query OK, 1 row affected (0.14 sec) mysql> insert into orderByMathCalculation(Quantity, Price) values(2, 20); Query ...
Read MoreHow to add column using alter in MySQL?\\n
Following is the syntax to add column using alter in MySQL:alter table yourTableName add column yourColumnName yourDataType default yourValue;Let us first create a table:mysql> create table alterTableDemo -> ( -> Id int, -> Name varchar(10) -> ); Query OK, 0 rows affected (0.69 sec)Let us check the description of the table using DESC command. This displays Field, Type, Key, etc. of the table:mysql> desc alterTableDemo;This will produce the following output+-------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+-------+ | Id | int(11) | YES ...
Read MoreHow to suppress MySQL stored procedure output?
To suppress MySQL stored procedure output, you can use variable. Let us first create a table.mysql> create table person_information -> ( -> Id int, -> Name varchar(20) -> ); Query OK, 0 rows affected (0.50 sec)Following is the query to insert some records in the table using insert command:mysql> insert into person_information values(100, 'John'); Query OK, 1 row affected (0.17 sec) mysql> insert into person_information values(101, 'Chris'); Query OK, 1 row affected (0.22 sec) mysql> insert into person_information values(102, 'Robert'); Query OK, 1 row affected (0.16 sec)Following is the query to display records from ...
Read MoreWrite a MySQL query equivalent to “SHOW TABLES” in sorted order?
Use INFORMATION_SCHEMA.TABLES to display tables in sorted order. The below syntax will give sorted list of tables in ascending order:select TABLE_NAME from INFORMATION_SCHEMA.TABLES where TABLE_SCHEMA= 'yourDatabaseName' order by TABLE_NAME;Following is the query to implement the equivalent to SHOW TABLES:mysql> select TABLE_NAME from INFORMATION_SCHEMA.TABLES -> where TABLE_SCHEMA= 'sample' order by TABLE_NAME;This will produce the following output+------------------------------------+ | TABLE_NAME | +------------------------------------+ | a | | accumulateddemo ...
Read MoreMySQL query to get the count of rows in which two or more specified values appear?\\n
To get the count of rows in which two or more specified values appear, let us first create a sample table:mysql> create table specifiedValuesDemo -> ( -> Value int, -> Value2 int, -> Value3 int -> ); Query OK, 0 rows affected (0.60 sec)Following is the query to insert some records in the table using insert command:mysql> insert into specifiedValuesDemo values(10, 15, 20); Query OK, 1 row affected (0.17 sec) mysql> insert into specifiedValuesDemo values(40, 10, 20); Query OK, 1 row affected (0.16 sec) ...
Read MoreHow to create double nested array in MongoDB?
To create a double nested array in MongoDB, let us implement the query to create a collection with documents. Within that, we have created a double nested array that displays Student Details, with the project name and technologies used to develop the same project:> db.doubleNestedArrayDemo.insertOne( ... { ... "StudentId" : "1000", ... "StudentName" : "Larry", ... "StudentDetails" : [ ... { ... "ProjectName" : "Online Banking", ... "ProjectDetails" : [ ... { ... "TechnologyUsed" : "Java" ... }, ... ...
Read MoreSort by character length in MySQL
To sort by character length in MySQL use the ORDER BY LENGTH(). Let us first create a table:mysql> create table orderingAADemo -> ( -> Value varchar(100) -> ); Query OK, 0 rows affected (1.30 sec)Following is the query to insert some records in the table using insert command:mysql> insert into orderingAADemo values('A'); Query OK, 1 row affected (0.12 sec) mysql> insert into orderingAADemo values('B'); Query OK, 1 row affected (0.13 sec) mysql> insert into orderingAADemo values('AA'); Query OK, 1 row affected (0.20 sec) mysql> insert into orderingAADemo values('C'); Query OK, 1 row affected (0.12 ...
Read MoreHow to convert bool to int in MySQL?\\n
To convert bool to int in MySQL, you can use CAST(). Let us first create a table:mysql> create table convertBoolToIntDemo -> ( -> isYoung bool -> ); Query OK, 0 rows affected (0.69 sec)Following is the query to insert some records in the table using insert command:mysql> insert into convertBoolToIntDemo values(true); Query OK, 1 row affected (0.18 sec) mysql> insert into convertBoolToIntDemo values(false); Query OK, 1 row affected (0.09 sec) mysql> insert into convertBoolToIntDemo values(true); Query OK, 1 row affected (0.15 sec) mysql> insert into convertBoolToIntDemo values(false); Query ...
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