To fix this error, you need to add PRIMARY KEY to auto_increment field. Let us now see how this error occurs −Here, we are creating a table and it gives the same error −mysql> create table DemoTable (    StudentId int NOT NULL AUTO_INCREMENT,    StudentName varchar(40),    StudentAge int ); ERROR 1075 (42000) : Incorrect table definition; there can be only one auto column and it must be defined as a keyTo solve the above error, you need to add PRIMARY KEY with AUTO_INCREMENT. Let us first create a table −mysql> create table DemoTable (    StudentId int NOT ... Read More

To change only dates, not time, use the MySQL INTERVAL and YEAR. Since, we will be updating the records, therefore, use UPDATE and set a new value with INTERVAL.Let us see an example and create a table −mysql> create table DemoTable (    DueDate datetime ); Query OK, 0 rows affected (0.56 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('2017-08-12 10 :30 :45'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values('2015-09-21 12 :00 :00'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable values('2018-12-31 11 :45 :56'); Query ... Read More

We need to find the weekday i.e. week 1 from date 1 to 7, week 2 from date 8 to 14, etc. To get the day, use DAY() function in MySQL. Set the conditions to get the weekday (number) using CASE statement.Let us now see an example and create a table −mysql> create table DemoTable (    AdmissionDate date ); Query OK, 0 rows affected (0.63 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('2019-09-12'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable values('2019-09-06'); Query OK, 1 row affected (0.16 sec) mysql> ... Read More

To fetch every alternative row, use MOD() under WHERE. Then use ORDER BY DESC to display the result in descending order −select *from yourTableName where mod(yourColumnName, 2)=1 order by yourColumnName DESC;Let us first create a table −mysql> create table DemoTable (    UniqueId int NOT NULL AUTO_INCREMENT PRIMARY KEY,    ClientName varchar(40),    ClientAge int ); Query OK, 0 rows affected (1.02 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(ClientName, ClientAge) values('Chris', 34); Query OK, 1 row affected (0.47 sec) mysql> insert into DemoTable(ClientName, ClientAge) values('Tom', 45); Query OK, 1 row affected (0.19 sec) mysql> ... Read More

To get the email addresses beginning with 5 numeric characters, the optional solution is to use REGEXP −select *from yourTableName where yourColumnName regexp "^[0-9]{5}";Let us first create a table −mysql> create table DemoTable (    UserEmailAddress varchar(100) ); Query OK, 0 rows affected (0.76 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('6574John@gmail.com'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values('Carol23456@gmail.com'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable values('98989Chris_45678@gmail.com'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable values('Mike12@gmail.com'); Query OK, 1 row affected (0.43 ... Read More

Let us first create a table −mysql> create table DemoTable (    Name varchar(40),    Score int ); Query OK, 0 rows affected (0.72 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('Chris Brown', 78); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values('John Doe', 88); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable values('Carol Taylor', 98); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values('David Miller', 80); Query OK, 1 row affected (0.68 sec)Display all records from the table using select statement −mysql> select *from ... Read More

You cannot directly use an alias in the SELECT. Instead, use a user-defined variable. Following is the syntax. Here, @yourAliasName is our variable and alias −select @yourAliasName :=curdate() as anyAliasName, concat(‘yourValue.', yourColumnName, ' yourValue', @yourAliasName) as anyAliasName from yourTableName;Let us first create a table −mysql> create table DemoTable (    Name varchar(40) ); Query OK, 0 rows affected (0.62 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('John Smith'); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable values('Chris Brown'); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable values('David Miller'); ... Read More

For this, simply use UPDATE command along with SET. Let us first create a table −mysql> create table DemoTable (    StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY,    StudentScore int ); Query OK, 0 rows affected (0.81 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(StudentScore) values(78); Query OK, 1 row affected (0.46 sec) mysql> insert into DemoTable(StudentScore) values(89); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable(StudentScore) values(67); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable(StudentScore) values(95); Query OK, 1 row affected (0.25 sec)Display all records from the table ... Read More

Following is the syntax −select date_format(yourColumnName, '%d/%m/%Y') as anyAliasName from yourTableName;Let us first create a table −mysql> create table DemoTable (    AdmissionDate date ); Query OK, 0 rows affected (0.89 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('2019-01-21'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable values('2019-09-09'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values('2018-12-31'); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable values('2017-11-01'); Query OK, 1 row affected (0.16 sec)Display all records from the table using select statement −mysql> select *from DemoTable;This ... Read More

Let us first create a table −mysql> create table DemoTable1219 (    Id int,    Name varchar(40) ); Query OK, 0 rows affected (0.43 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1219 values(100, 'Adam'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable1219 values(101, 'John'); Query OK, 1 row affected (0.23 sec) mysql> insert into DemoTable1219 values(102, 'Chris'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable1219 values(103, 'Bob'); Query OK, 1 row affected (0.18 sec)Display all records from the table using select statement −mysql> select *from DemoTable1219;This will produce the ... Read More