Use group_concat() function from MySQL to concatenate. Let us first create a table −mysql> create table DemoTable    -> (    -> Subject varchar(10)    -> ); Query OK, 0 rows affected (0.43 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('C'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable values('C++'); Query OK, 1 row affected (0.25 sec) mysql> insert into DemoTable values('C++'); Query OK, 1 row affected (0.06 sec) mysql> insert into DemoTable values('MongoDB'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable values('MySQL'); Query ... Read More

To order by number of chars, use ORDER BY and LENGTH() method. Following is the syntax −select *from yourTableName order by LENGTH(yourColumnName) DESC;Let us first create a table −mysql− create table DemoTable    -> (    -> Name varchar(100)    -> ); Query OK, 0 rows affected (0.50 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('John'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable values('Robert'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values('Bob'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable ... Read More

To update an existing table, use UPDATE. With that, to set the current date, use the CURDATE() method −update yourTableName set yourCoumnName=CURDATE();Let us first create a table −mysql> create table DemoTable -> ( -> DueDate datetime -> ); Query OK, 0 rows affected (0.58 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('2019-01-10') ; Query OK, 1 row affected (0.21 sec) mysql> insert into DemoTable values('2019-03-31'); Query OK, 1 row affected (0.18 sec)Display all records from the table using select statement −mysql> select *from DemoTable;OutputThis will produce the following output −+---------------------+ | DueDate ... Read More

Use SUBSTRING_INDEX to select everything before @ in an email-id −select substring_index(yourColumnName, '@', 1) from yourTableName;Let us first create a table −mysql> create table DemoTable -> ( -> EmployeeMailId varchar(100) -> ); Query OK, 0 rows affected (0.52 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('Larry123@gmail.com'); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable values('987Sam@hotmail.com'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values('123456David_98@gmail.com'); Query OK, 1 row affected (0.20 sec)Display all records from the table using select statement −mysql> select *from DemoTable;OutputThis will produce the ... Read More

To set default field value, use the “default”. Let us first create a table −mysql> create table DemoTable -> ( -> Age int -> ); Query OK, 0 rows affected (0.58 sec)Here is the query to set default field value in MySQL −mysql> alter table DemoTable MODIFY Age int default 18; Query OK, 0 rows affected (0.25 sec) Records: 0 Duplicates: 0 Warnings: 0Now you can check the table description −mysql> desc DemoTable;OutputThis will produce the following output −+-------+---------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+---------+------+-----+---------+-------+ | Age ... Read More

Let us first create a table −mysql> create table DemoTable -> ( -> Amount int, -> SubTotal int -> ); Query OK, 0 rows affected (0.65 sec)Insert some records in the table using insert command −ysql> insert into DemoTable(Amount) values(50); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable(Amount) values(60); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable(Amount) values(70); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable(Amount) values(80); Query OK, 1 row affected (0.17 sec)Display all records from the table using select statement −mysql> select *from DemoTable;OutputThis will produce ... Read More

For this, you can use UNIQUE INDEX −alter table yourTableName ADD UNIQUE INDEX(yourColumnName1, yourColumnName2, ....N);Let us first create a table −mysql> create table DemoTable    -> (    -> Value1 int,    -> Value2 int    -> ); Query OK, 0 rows affected (0.55 sec)Following is the query to add unique index −mysql> alter table DemoTable ADD UNIQUE INDEX(Value1, Value2); Query OK, 0 rows affected (0.54 sec) Records: 0  Duplicates: 0  Warnings: 0Insert some records in the table using insert command −Note − Use the INSERT IGNORE command rather than the INSERT command. If a record doesn't duplicate an existing ... Read More

Use the STR_TO_DATE() method for this. Let us first create a table −mysql> create table DemoTable -> ( -> DueDatetime varchar(100) -> ); Query OK, 0 rows affected (1.03 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('22-06-2019 14:40'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable values('02-07-2015 13:10'); Query OK, 1 row affected (0.18 sec)Display all records from the table using select statement −mysql> select *from DemoTable;OutputThis will produce the following output −+------------------+ | DueDatetime | +------------------+ | 22-06-2019 14:40 | | 02-07-2015 13:10 | ... Read More

Yes, you can use LEAST() function from MySQL −select least(yourColumnName1, yourColumnName2, ...N) from yourTableName;Let us first create a table −mysql> create table DemoTable    -> (    -> Date1 date,    -> Date2 date,    -> Date3 date    -> ); Query OK, 0 rows affected (0.54 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('2019-03-31', '2019-01-01', '2019-03-05'); Query OK, 1 row affected (0.17 sec)Display all records from the table using select statement −mysql> select *from DemoTable;OutputThis will produce the following output −+------------+------------+------------+ | Date1      | Date2 | ... Read More

Since “select” is a reserved word in MySQL, we cannot create a table name with it. But, if you still want to create such a table, surround the word select with quote.Let us first create a table −mysql> create table `select` -> ( -> Number int -> ); Query OK, 0 rows affected (0.79 sec)Insert some records in the table using insert command −mysql> insert into `select` values(10); Query OK, 1 row affected (0.16 sec) mysql> insert into `select` values(20); Query OK, 1 row affected (0.11 sec) mysql> insert into `select` values(30); Query OK, 1 row affected (0.12 ... Read More