Let us first see when this situation can arise. Create a table and set column name with datatype but without the size −mysql> create table DemoTable (    Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,    FirstName varchar,    LastName varchar ); ERROR 1064 (42000): You have an error in ... Read More

To use the reserved keyword ‘Key’, use the concept of the backtick symbol. Here, for our example, I am using the column name key which needs a backtick symbol around the column name.Let us first create a table −mysql> create table DemoTable (    `Key` int ); Query OK, 0 ... Read More

Let us first create a table −mysql> create table DemoTable (    Money DECIMAL(7, 2) ); Query OK, 0 rows affected (0.58 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(100.67); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable values(199.33); Query OK, ... Read More

For this, you can use GROUP BY HAVING clause. Let us first create a table −mysql> create table DemoTable (    Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,    Value int ); Query OK, 0 rows affected (0.52 sec)Insert some records in the table using insert command −mysql> insert into ... Read More

For this, use JSON_OBJECTAGG(). Let us first create a table −mysql> create table DemoTable (    Id int,    FirstName varchar(100),    Age int ); Query OK, 0 rows affected (0.56 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(10, 'John', 23); Query OK, 1 ... Read More

Let us first create a table −mysql> create table DemoTable (    Logouttime time ); Query OK, 0 rows affected (0.62 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('5:50:00'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values('6:10:10'); Query OK, 1 ... Read More

For this, you can use the aggregate function SUM(). Let us first create a table −mysql> create table DemoTable (    isMarried tinyint(1) ); Query OK, 0 rows affected (0.84 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(0); Query OK, 1 row affected (0.26 ... Read More

Let’s say you have set dates in the VARCHAR format. Now if you want to update the format, then use the UPDATE command along with STR_TO_DATE(). The syntax is as follows −update yourTableName set yourColumnName=str_to_date(yourColumnName, '%m/%d/%Y');Let us first create a table −mysql> create table DemoTable (    DueDate varchar(100) ); ... Read More

Let us first create a table −mysql> create table DemoTable (    isValidUser boolean ); Query OK, 0 rows affected (0.70 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(true); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable values(false); Query OK, 1 ... Read More

Let us first create a table −mysql> create table DemoTable (    FirstDate datetime,    SecondDate datetime ); Query OK, 0 rows affected (0.57 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('2019-01-21', '2018-01-21'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable ... Read More