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MySQL Articles
Page 304 of 355
Get the count of only unique rows in a MySQL column?
In MySQL, COUNT() will display the number of rows. DISTINCT is used to ignore duplicate rows and get the count of only unique rows.Let us first create a table:mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, FirstName varchar(10) ); Query OK, 0 rows affected (0.47 sec)Following is the query to insert some records in the table using insert command:mysql> insert into DemoTable(FirstName) values('Larry'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable(FirstName) values('John'); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable(FirstName) values('Sam'); Query OK, 1 row affected (0.13 sec) ...
Read MoreMySQL query to get sum of each column where every column has same number of values?
You can use aggregate function SUM() for this. Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, FirstValue int, SecondValue int, ThirdValue int ); Query OK, 0 rows affected (0.57 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(FirstValue, SecondValue, ThirdValue) values(10, 20, 30); Query OK, 1 row affected (0.22 sec) mysql> insert into DemoTable(FirstValue, SecondValue, ThirdValue) values(60, 50, 40); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable(FirstValue, SecondValue, ThirdValue) values(80, 90, 100); Query OK, 1 row affected ...
Read MoreCan I use SUM() with IF() in MySQL?
Yes, you can use SUM() with IF() in MySQL. Let us first create a demo table:mysql> create table DemoTable ( Value int, Value2 int ); Query OK, 0 rows affected (0.51 sec)Following is the query to insert some records in the table using insert command:mysql> insert into DemoTable values(100, 400); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values(100, 400); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values(400, 100); Query OK, 1 row affected (0.14 sec)Following is the query to display records from the table using select command:mysql> select *from DemoTable;This ...
Read MoreDo Double Equal Sign exist in MySQL?
There is no double equal sign concept. It can be used to compare two values. If you use double equal sign(==) in MySQL, you will get an error message.Let us verify the concept is true or not. Declare a variable −mysql> set @Number=10; Query OK, 0 rows affected (0.00 sec)Now, compare the above variable value with 10. If both the values are same then the result will be 1 otherwise 0.Using double equal sign −mysql> select 10==@Number;This will produce the following output i.e. an error −ERROR 1064 (42000): You have an error in your SQL syntax; check the manual ...
Read MoreDelete last 4 letters in MySQL?
You can use SUBSTRING() along with UPDATE command to delete last 4 letters. Let us first create a table −mysql> create table DemoTable ( StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, StudentSubject varchar(100) ); Query OK, 0 rows affected (0.57 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(StudentSubject) values('Introduction to Java'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable(StudentSubject) values('Introduction to C'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable(StudentSubject) values('Introduction to C++'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable(StudentSubject) values('Spring And Hibernate'); ...
Read MoreChange tinyint default value to 1 in MySQL?
You can use DEFAULT command for this. Following is the syntax −alter table yourTableName change yourColumnName yourColumnName TINYINT(1) DEFAULT 1 NOT NULL;Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, UserName varchar(20), UserAge int, isMarried tinyint(1) ); Query OK, 0 rows affected (0.80 sec)Let us check the description of table −mysql> desc DemoTable;This will produce the following output −+-----------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------+-------------+------+-----+---------+----------------+ | Id ...
Read MoreHow to multiply columns and then sum the rows with similar records like customer name?
To understand this, let us create a table with fields like ID, Customer Name, Items, Price. We will first multiply the items with price. After that the rows with similar records i.e. same customer name will get added.Let us first create a table:mysql> create table DemoTable ( CustomerId int NOT NULL AUTO_INCREMENT PRIMARY KEY, CustomerName varchar(100), CustomerItems int, CustomerPrice int ); 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 DemoTable(CustomerName, CustomerItems, CustomerPrice)values('Larry', 3, 450); Query OK, 1 row affected (0.24 sec) mysql> ...
Read MoreHow to export specific column data in MySQL?
To export specific column data in MySQL, use OUTFILE −select yourColumnName from yourTableName into outfile 'yourLocationOfFile’;Let us first create a table −mysql> create table DemoTable ( StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, StudentFirstName varchar(20), StudentLastName varchar(20) ); Query OK, 0 rows affected (0.54 sec)Insert records in the table using insert command −mysql> insert into DemoTable(StudentFirstName, StudentLastName) values('John', 'Doe'); Query OK, 1 row affected (0.26 sec) mysql> insert into DemoTable(StudentFirstName, StudentLastName) values('David', 'Miller'); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable(StudentFirstName, StudentLastName) values('John', 'Smith'); Query OK, 1 row affected (0.15 sec) mysql> insert into ...
Read MoreGet count of values that only appear once in a MySQL column?
To get number of values that only appear once in a column, use GROUP BY HAVING. Let us first create a table:mysql> create table DemoTable ( Name varchar(20) ); Query OK, 0 rows affected (0.55 sec)Following is the query to insert some records in the table using insert command:mysql> insert into DemoTable values('Larry'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values('Larry'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable values('Sam'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values('Chris'); Query OK, 1 row affected (0.14 sec) mysql> insert into ...
Read MoreFinding only strings beginning with a number using MySQL Regex?
To find strings beginning with a number, use Regular Expressions. Let us first create a table −mysql> create table DemoTable ( Id varchar(200) ); Query OK, 0 rows affected (0.59 sec)Insert records in the table using insert command −mysql> insert into DemoTable values('123User'); Query OK, 1 row affected (0.22 sec) mysql> insert into DemoTable values('_$123User'); Query OK, 1 row affected (0.22 sec) mysql> insert into DemoTable values('User123456'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values('0000User'); Query OK, 1 row affected (0.22 sec) mysql> insert into DemoTable values('&^*User'); Query OK, 1 row affected (0.24 sec)Display records ...
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