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Database Articles
Page 423 of 547
How to return distinct values in MySQL and their count?
To return only the distinct values, use GROUP BY clause.Let us first create a table −mysql> create table DemoTable754 (ProductPrice int); Query OK, 0 rows affected (0.48 sec)Insert some records in the table using insert command −mysql> insert into DemoTable754 values(200); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable754 values(500); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable754 values(200); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable754 values(500); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable754 values(800); Query OK, 1 row affected (0.24 sec) mysql> insert into DemoTable754 ...
Read MoreMySQL query to ORDER BY `user_id` IN (1,2,3) AND `name` for custom ordering
To implement IN() for custom ordering, use ORDER BY CASE.Let us first create a table −mysql> create table DemoTable752 ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, Name varchar(100) ); Query OK, 0 rows affected (0.63 sec)Insert some records in the table using insert command −mysql> insert into DemoTable752(Name) values('John'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable752(Name) values('Carol'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable752(Name) values('Bob'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable752(Name) values('Mike'); Query OK, 1 row affected (0.23 sec) mysql> insert into DemoTable752(Name) values('Sam'); ...
Read MoreGet all the records with two different values in another column with MySQL
For this, you can use GROUP BY HAVING clause.Let us first create a table −mysql> create table DemoTable751 ( StudentName varchar(100), SubjectName varchar(100) ); Query OK, 0 rows affected (0.66 sec)Insert some records in the table using insert command −mysql> insert into DemoTable751 values('John', 'MySQL'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable751 values('John', 'MongoDB'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable751 values('Sam', 'MySQL'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable751 values('Carol', 'Java'); Query OK, 1 row affected (0.21 sec) mysql> insert into DemoTable751 values('David', 'MySQL'); ...
Read MoreSelect records from a table on the basis of keywords in MySQL
Let’s say some of the columns values in a table has a specific keyword and you want only those records. For this, use the LIKE operator.Let us first see an example and create a table −mysql> create table DemoTable750 (Title varchar(200)); Query OK, 0 rows affected (0.69 sec)Insert some records in the table using insert command −mysql> insert into DemoTable750 values('Java and MongoDB, MySQL'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable750 values('MySQL, SQL Server'); Query OK, 1 row affected (0.21 sec) mysql> insert into DemoTable750 values('PL/SQL, Python, MongoDB'); Query OK, 1 row affected (0.14 sec) mysql> ...
Read MoreList logged-in MySQL users?
To list logged-in MySQL users, you can use any of the following two methods −First MethodUse INFORMATION_SCHEMA.PROCESSLISTselect *from INFORMATION_SCHEMA.PROCESSLIST;Second MethodYou can use SHOW PROCESSLIST command as well. Following is the syntax −SHOW PROCESSLIST;Let us implement the above syntaxes in order to list logged in MySQL users −mysql> select *from information_schema.processlist;This will produce the following output -+----+-----------------+-----------------+------+---------+--------+-----------------------------+---------------------------------------------+ | ID | USER | HOST | DB | COMMAND | TIME | STATE | INFO ...
Read MoreUpdate all the zero values with a custom value in MySQL with a function similar to ISNULL()
For this, you can use custom IF() and set a value whenever 0 appears.Let us first create a table −mysql> create table DemoTable749 (Value int); Query OK, 0 rows affected (1.02 sec)Insert some records in the table using insert command −mysql> insert into DemoTable749 values(10); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable749 values(0); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable749 values(769); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable749 values(0); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable749 values(78); Query OK, 1 row affected (0.14 sec) ...
Read MoreMySQL query to extract only the day instead of entire date
To extract only the day instead of the entire date, you need to use DAYOFMONTH() function from MySQL.Let us first create a table −mysql> create table DemoTable747 (DueDate datetime); Query OK, 0 rows affected (0.53 sec)Insert some records in the table using insert command −mysql> insert into DemoTable747 values('2019-01-31') ; Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable747 values('2018-12-01'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable747 values('2017-09-14'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable747 values('2016-07-21'); Query OK, 1 row affected (0.14 sec)Display all records from the table using select ...
Read MoreMySQL query to display only the empty and NULL values together?
To check for NULL, use the IS NULL. For empty values, you need to check with an empty string. We will now see an example.Let us first create a table −mysql> create table DemoTable691( PlayerId int NOT NULL AUTO_INCREMENT PRIMARY KEY, PlayerName varchar(100), PlayerScore int ); Query OK, 0 rows affected (0.56 sec)Insert some records in the table using insert command −mysql> insert into DemoTable691(PlayerName, PlayerScore) values('Robert', 56); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable691(PlayerName, PlayerScore) values('David', 89); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable691(PlayerName, PlayerScore) values('', 98); Query ...
Read MoreWill "create table table" work in MySQL since we cannot use reserved words as table name?
Let us first see a case wherein we use “create table table” while creating a table. An error will arise −mysql> create table table( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, FirstName varchar(100) );This will produce the following output i.e. error −ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'table( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, FirstName varchar(100) )' at line 1As you can see above, the word “table” is a reserved keyword, and we ...
Read MoreHow to select records that begin with a specific value in MySQL?
To select records that begin with a specific value, you need to use LIKE operator. Let us first create a table −mysql> create table DemoTable690( UserId int NOT NULL AUTO_INCREMENT PRIMARY KEY, UserValue varchar(100) ); Query OK, 0 rows affected (0.56 sec)Insert some records in the table using insert command −mysql> insert into DemoTable690(UserValue) values('567890'); Query OK, 1 row affected (0.21 sec) mysql> insert into DemoTable690(UserValue) values('789032'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable690(UserValue) values('567342'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable690(UserValue) values('890678'); Query OK, 1 row affected (0.16 sec)Display ...
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