Let us first create a table −mysql> create table DemoTable    -> (    -> Name varchar(100),    -> Code varchar(100)    -> ); Query OK, 0 rows affected (0.54 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('Chris', '0001'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable values('Robert', '0002'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable values('Robert', '0003'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values('Chris', '0001'); Query OK, 1 row affected (0.12 sec)Display all records from the table using ... Read More

To delete all rows older than 30 days, you need to use the DELETE with INTERVAL. Use < now() i.e. less than operator to get all the records before the current date.Let us first create a table −mysql> create table DemoTable    -> (    -> UserMessage text,    -> UserMessageSentDate date    -> ); Query OK, 0 rows affected (0.59 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('Hi', '2019-06-01'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable values('Hello', '2019-07-02'); Query OK, 1 row affected (0.14 sec) mysql> insert ... Read More

You can use having clause. Let us first create a table −mysql> create table DemoTable    -> (    -> AdmissionDate varchar(100)    -> ); Query OK, 0 rows affected (0.55 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('10/12/2017'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values('01/11/2018'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable values('31/01/2019'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values('09/06/2019'); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable values('19/04/2019'); Query OK, 1 ... Read More

For this, you can use DATEDIFF(). Let us first create a table −mysql> create table DemoTable -> ( -> ShippingDate datetime -> ); Query OK, 0 rows affected (0.90 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('2019-07-01'); Query OK, 1 row affected (0.29 sec) mysql> insert into DemoTable values('2019-07-02'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values('2019-07-03'); Query OK, 1 row affected (0.32 sec) mysql> insert into DemoTable values('2019-07-04'); Query OK, 1 row affected (0.15 sec)Display all records ... Read More

Yes, you can use json_extract(). Let us first create a table −mysql> create table DemoTable    -> (    -> Data json    -> ); Query OK, 0 rows affected (0.63 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('{"Name": "John", "CountryName": "US"}'); Query OK, 1 row affected (0.33 sec) mysql> insert into DemoTable values('{"Name": "Chris", "CountryName": "UK"}'); Query OK, 1 row affected (0.15 sec)Display all records from the table using select statement −mysql> select *from DemoTable;Output+----------------------------------------+ | Data                               ... Read More

To get the highest value, use the GREATEST() method. Let us first create a table −mysql> create table DemoTable    -> (    -> Value1 int,    -> Value2 int,    -> Value3 int    -> ); Query OK, 0 rows affected (1.29 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(100, 600, 400); Query OK, 1 row affected (0.19 sec)Display all records from the table using select statement −mysql> select *from DemoTable;Output+--------+--------+--------+ | Value1 | Value2 | Value3 | +--------+--------+--------+ | 100 | 600 | 400    | ... Read More

For this, use IF(). Let us first create a table −mysql> create table DemoTable    -> (    -> PlayerName varchar(100),    -> PlayerScore int,    -> PlayerStatus varchar(100)    -> ); Query OK, 0 rows affected (0.58 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('John', 88, 'BAD'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values('Chris', 78, 'BAD'); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable values('Robert', 90, 'BAD'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values('David', 80, 'BAD'); Query ... Read More

To get the first two highest columns, use ORDER BY. With that, use LIMIT 2 to get only the first 2 −select *from yourTableName order by yourColumnName DESC LIMIT 2;Let us first create a table −mysql> create table DemoTable    -> (    -> Value int    -> ); Query OK, 0 rows affected (0.54 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(90); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values(70); Query OK, 1 row affected (0.28 sec) mysql> insert into DemoTable values(40); Query OK, 1 row affected ... Read More

To find a row, use FIND_IN_SET(). Let us first create a table −mysql> create table DemoTable    -> (    -> ListOfIds varchar(200)    -> ); Query OK, 0 rows affected (0.72 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('100, 2093, 678, 686'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable values('0595, 9585, 4885, 95959'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable values('0059954, 95986884, 9059596, 9005'); Query OK, 1 row affected (0.20 sec)Display all records from the table using select statement −mysql> select *from DemoTable;Output+-------------------------------+ ... Read More

Following is the syntax −show variables where Variable_name like 'yourVariable1%' or Variable_name like 'yourVariable2%', .............N;Let us implement the above syntax to show(more than one) variables −mysql> show variables where Variable_name like 'key%' or Variable_name like 'innodb_undo%' or Variable_name like 'innodb_log%';Output+------------------------------------+----------+ | Variable_name                      | Value | +------------------------------------+----------+ | innodb_log_buffer_size             | 1048576 | | innodb_log_checksums               | ON | | innodb_log_compressed_pages        | ON ... Read More