Let us first create a table −mysql> create table DemoTable (    ClientId int NOT NULL AUTO_INCREMENT PRIMARY KEY,    ClientName varchar(40),    ClientAge int,    ClientCountryName varchar(40) ); Query OK, 0 rows affected (0.57 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(ClientName, ClientAge, ClientCountryName) ... Read More

To make a date column null, use ALTER TABLE and MODIFY and set the date to NULL. Following is the syntax −alter table yourTableName modify column yourColumnName date NULL;Let us first create a table. Here, we have set the column as NOT NULL −mysql> create table DemoTable (    ShippingDate ... Read More

The syntax is as follows to get the column names of a table −select column_name from information_schema.columns where table_schema='yourDatabaseName' and table_name=’yourTableName’;Let us first create a table −mysql> create table DemoTable (    EmployeeId int,    EmployeeFirstName varchar(20),    EmployeeLastName varchar(20),    EmployeeAge int,    EmployeeCountryName varchar(40),    IsMarried tinyint(1),   ... Read More

To check if field of a table has NOT NULL property, you can use any of the two syntaxes. The first syntax is as follows −desc yourTableName;Following is the second syntax −select column_name,    is_nullable    from information_schema.columns    where table_schema = ‘yourDatabaseName’    and table_name = 'yourTableName’;Let us first ... Read More

To prevent a combination of items from being inserted twice, alter the table and set UNIQUE for the column as shown in the below syntax −alter table yourTableName add constraint yourConstraintName unique(yourColumnName1, yourColumnName2, ....N);Let us first create a table −mysql> create table DemoTable (    Value1 int,    Value2 int ... Read More

For this, use BETWEEN -1 AND 1. Let us first create a table −mysql> create table DemoTable (    Value int ); Query OK, 0 rows affected (0.76 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(14); Query OK, 1 row affected (0.15 sec) mysql> ... Read More

For this, you need to use UNIQUE KEY for the column. Let us first create a table −mysql> create table DemoTable (    Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,    FirstName varchar(30),    UNIQUE KEY(FirstName) ); Query OK, 0 rows affected (1.76 sec)Insert some records in the table using ... Read More

Let us first create a table −mysql> create table DemoTable (    ProductAmount int,    PurchaseDate datetime ); Query OK, 0 rows affected (0.94 sec)Note − Let’s say the current date is 2010-09-15.Insert some records in the table using insert command −mysql> insert into DemoTable values(567, '2019-09-10'); Query OK, 1 ... Read More

Let us first create a table −mysql> create table DemoTable (    Subject text ); Query OK, 0 rows affected (0.86 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('Introduction to MySQL'); Query OK, 1 row affected (0.31 sec) mysql> insert into DemoTable values('Deep Dive ... Read More

Let us first create a table −mysql> create table DemoTable (    Joiningdate date ); Query OK, 0 rows affected (0.56 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('2010-01-01'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable values('2010-03-31'); Query OK, 1 ... Read More