Database Articles

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MySQL search and replace record from a list of records

AmitDiwan
AmitDiwan
Updated on 13-Dec-2019 165 Views

Let us first create a table −mysql> create table DemoTable    -> (    -> ListOfName text    -> ); Query OK, 0 rows affected (0.66 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('Carol, Sam, John, David, Bob, Mike, Robert, John, Chris, James, Jace'); Query OK, 1 row affected (0.13 sec)Display all records from the table using select statement −mysql> select *from DemoTable;This will produce the following output −+------------------------------------------------------------+ | ListOfName                                               ...

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How to extract date from string in MySQL?

AmitDiwan
AmitDiwan
Updated on 13-Dec-2019 777 Views

To extract date from the string in MySQL, use SUBSTRING_INDEX(). Let us first create a table −mysql> create table DemoTable    -> (    -> Title text    -> ); Query OK, 0 rows affected (0.58 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('John has got joining date.12/31/2018'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values('Carol has got joining date.01/11/2019'); Query OK, 1 row affected (0.22 sec) mysql> insert into DemoTable values('Sam will arrive at.12/03/2050'); Query OK, 1 row affected (0.87 sec)Display all records from the table using select statement ...

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MySQL query to find the number of occurrences from two columns?

AmitDiwan
AmitDiwan
Updated on 13-Dec-2019 524 Views

Use MySQL GROUP_BY to find the number of occurrences from two columns. Let us first create a table −mysql> create table DemoTable    -> (    -> Name1 varchar(20),    -> Name2 varchar(20)    -> ); Query OK, 0 rows affected (0.61 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('John', 'Adam'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values('Chris', 'David'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable values('Robert', 'Mike'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values('David', 'Chris'); Query OK, 1 row ...

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Find the difference between dates in the form of months with MySQL

AmitDiwan
AmitDiwan
Updated on 13-Dec-2019 2K+ Views

Let us first create a table −mysql> create table DemoTable    -> (    -> Date1 date,    -> Date2 date    -> ); Query OK, 0 rows affected (1.04 sec)Insert some records in the table using insert command &miuns;mysql> insert into DemoTable values('2017-01-10', '2017-12-10'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values('2018-12-31', '2015-01-02'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable values('2020-03-01', '2019-06-15'); Query OK, 1 row affected (0.19 sec)Display all records from the table using select statement −mysql> select *from DemoTable;This will produce the following output −+------------+------------+ | Date1     ...

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How to use ORDER BY field and sort by id in a single MySQL field?

AmitDiwan
AmitDiwan
Updated on 13-Dec-2019 728 Views

For this, you can use ORDER BY FIELD. Let us first create a table −mysql> create table DemoTable    -> (    -> Id int,    -> Name varchar(20)    -> ); Query OK, 0 rows affected (1.78 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(101, 'Chris'); Query OK, 1 row affected (0.38 sec) mysql> insert into DemoTable values(201, 'Mike'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values(110, 'Adam'); Query OK, 1 row affected (0.52 sec) mysql> insert into DemoTable values(250, 'John'); Query OK, 1 row affected (0.33 sec)Display all ...

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Select distinct values from three columns and display in a single column with MySQL

AmitDiwan
AmitDiwan
Updated on 13-Dec-2019 592 Views

For this, use UNION more than once in a single MySQL query. Let us first create a table −mysql> create table DemoTable    -> (    -> Value1 int,    -> Value2 int,    -> Value3 int    -> ); Query OK, 0 rows affected (0.69 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(20, null, null); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable values(20, null, null); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable values(20, null, null); Query OK, 1 row affected (0.12 sec) mysql> insert into ...

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Implement MySQL CASE statement with WHEN clause

AmitDiwan
AmitDiwan
Updated on 13-Dec-2019 264 Views

CASE statement with the WHEN clause is used to work around conditions. Following is the syntax−select *,    case when yourCondition then yourStatement    when yourCondition then yourStatement    .    . else yourStatement from yourTableName;Let us first create a table −mysql> create table DemoTable    -> (    -> StudentName varchar(20),    -> StudentMarks int    -> ); Query OK, 0 rows affected (0.77 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('Chris', 78); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable values('Robert', 88); Query OK, 1 row affected (0.14 sec) ...

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Which technique is more efficient for replacing duplicate records in MySQL?

AmitDiwan
AmitDiwan
Updated on 13-Dec-2019 148 Views

To replace duplicate records and avoid any error while inserting, use INSERT ON DUPLICATE KEY UPDATE. Let us first create a table −mysql> create table DemoTable    -> (    -> Id int,    -> Name varchar(20),    -> UNIQUE(Id, Name)    -> ); Query OK, 0 rows affected (0.78 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(101, 'Chris') on duplicate key update Id=10001, Name='Robert'; Query OK, 1 row affected (0.23 sec) mysql> insert into DemoTable values(102, 'Mike') on duplicate key update Id=10001, Name='Robert'; Query OK, 1 row affected (0.17 sec) mysql> insert into ...

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In MySQL, is there a way to turn column records into a list?

AmitDiwan
AmitDiwan
Updated on 13-Dec-2019 3K+ Views

Yes, we can turn a column records into a list using the MySQL GROUP_CONCAT(). Let us first create a table −mysql> create table DemoTable    -> (    -> ClientId int,    -> ClientName varchar(20)    -> ); Query OK, 0 rows affected (0.88 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(100, 'Chris'); Query OK, 1 row affected (0.54 sec) mysql> insert into DemoTable values(100, 'Robert'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values(100, 'Adam'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values(100, 'David'); Query OK, ...

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Create a temporary table with dates in MySQL

AmitDiwan
AmitDiwan
Updated on 13-Dec-2019 747 Views

To create a temporary table with dates, use the CREATE TEMPORARY TABLE in MySQL. Following is the syntax −Syntaxcreate temporary table yourTableName(    yourColumnName datetime );Let us first create a table −mysql> create temporary table DemoTable    -> (    -> DueDate datetime    -> ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(now()); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable values(curdate()); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable values('2018-01-21'); Query OK, 1 row affected (0.00 sec) mysql> insert into ...

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