Database Articles

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Find duplicate column values in MySQL and display them

AmitDiwan
AmitDiwan
Updated on 26-Dec-2019 730 Views

For this, use GROUP BY HAVING clause. Let us first create a table −mysql> create table DemoTable1858      (      ModelNumber varchar(50)      ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1858 values('Audi A4'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1858 values('Audi A6'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1858 values('Audi A4'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1858 values('Audi Q5'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1858 values('Audi R8'); ...

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MySQL query to get all characters before a specific character hyphen

AmitDiwan
AmitDiwan
Updated on 26-Dec-2019 1K+ Views

For this, you can use SUBSTRING_INDEX(). Let us first create a table −mysql> create table DemoTable1857      (      Name varchar(20)      ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1857 values('John-Smith'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1857 values('Brown-Chris'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1857 values('David-Carol-Miller'); Query OK, 1 row affected (0.00 sec)Display all records from the table using select statement −mysql> select * from DemoTable1857; This will produce the following output −+--------------------+ | Name   ...

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Using GROUP_CONCAT() on bit fields returns garbage in MySQL? How to fix?

AmitDiwan
AmitDiwan
Updated on 26-Dec-2019 207 Views

To fix, use group_concat() with addition of 0 with column. Let us first create a table −mysql> create table DemoTable1856      (      Id int,      Value bit(1)      ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1856 values(101, 1); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1856 values(102, 0); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1856 values(101, 0); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1856 values(102, 1); Query OK, 1 row affected (0.00 ...

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Which MySQL Datatype should be used for storing BloodType?

AmitDiwan
AmitDiwan
Updated on 26-Dec-2019 1K+ Views

To store BloodType, use varchar(3) or ENUM. Let us first create a table −mysql> create table DemoTable1855      (      BloodType varchar(3)      ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1855 values('A+'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1855 values('A-'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1855 values('B+'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1855 values('B-'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1855 values('AB+'); Query OK, 1 row affected ...

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Distinct number of specific items in list with MySQL

AmitDiwan
AmitDiwan
Updated on 26-Dec-2019 234 Views

To find distinct number of specific items, use COUNT() along with GROUP BY clause. Let us first create a table −mysql> create table DemoTable1854      (      Name varchar(20)      ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1854 values('John-Smith'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1854 values('Chris-Brown'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1854 values('Adam-Smith'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1854 values('John-Doe'); Query OK, 1 row affected (0.00 sec) mysql> insert into ...

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Why does comparing types in MySQL won't raise an error?

AmitDiwan
AmitDiwan
Updated on 26-Dec-2019 181 Views

If you try to compare string to int, MySQL won’t raise an error because it converts string to int. Let us first create a table −mysql> create table DemoTable1852      (      Value1 varchar(20),      Value2 int      ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1852 values('1John', 1); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1852 values('John', 1); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1852 values('1', 1); Query OK, 1 row affected (0.00 sec) mysql> insert into ...

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Delete records where timestamp older than 5 minutes in MySQL?

AmitDiwan
AmitDiwan
Updated on 26-Dec-2019 2K+ Views

For this, use DELETE command. Let us first create a table −mysql> create table DemoTable1851      (      DueDate datetime      ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1851 values('2019-12-03 21:30:35'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1851 values('2019-12-03 21:45:00'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1851 values('2019-12-03 21:34:00'); Query OK, 1 row affected (0.00 sec)Display all records from the table using select statement −mysql> select * from DemoTable1851; This will produce the following output −+---------------------+ | ...

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MySQL IF() to display custom YES or NO messages

AmitDiwan
AmitDiwan
Updated on 26-Dec-2019 745 Views

Let us first create a table −mysql> create table DemoTable1850      (      OrderStatus varchar(20)      ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1850 values('Yes'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1850 values('No'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1850 values('Yes'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1850 values('Yes'); Query OK, 1 row affected (0.00 sec)Display all records from the table using select statement −mysql> select * from DemoTable1850; This will produce the ...

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MySQL query to replace null value with empty string in several columns while fetching data

AmitDiwan
AmitDiwan
Updated on 26-Dec-2019 2K+ Views

For this, you can use IFNULL() or COALESCE(). Let us first create a table −mysql> create table DemoTable1849      (      ClientFirstName varchar(20),      ClientLastName varchar(20)      ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1849 values('John', NULL); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1849 values(NULL, 'Miller'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1849 values(NULL, NULL); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1849 values('Chris', 'Brown'); Query OK, 1 row affected (0.00 sec)Display all ...

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Add user defined value to a column in a MySQL query?

AmitDiwan
AmitDiwan
Updated on 26-Dec-2019 509 Views

Let us first create a table −mysql> create table DemoTable1847      (      GameStatus ENUM('PENDING', 'COMPLETED', 'CANCELLED')      ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1847 values('PENDING'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1847 values('COMPLETED'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1847 values('CANCELLED'); Query OK, 1 row affected (0.00 sec)Display all records from the table using select statement −mysql> select * from DemoTable1847; This will produce the following output −+------------+ | GameStatus | +------------+ | PENDING   ...

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