To set NOT NULL attribute to an existing column, use ALTER TABLE command. Let us first create a table −mysql> create table DemoTable1949    (    UserId int,    UserName varchar(20)    ); Query OK, 0 rows affected (0.00 sec)Here is the query to set NOT NULL attribute to an existing column −mysql> alter table DemoTable1949 modify UserName varchar(20) not null; Query OK, 0 rows affected (0.00 sec) Records: 0  Duplicates: 0  Warnings: 0Let us check the description of table −mysql> desc DemoTable1949;This will produce the following output −+----------+-------------+------+-----+---------+-------+ | Field    | Type        | Null | ... Read More

To sort only numbers from alphanumeric string, use ORDER BY RIGHT(). Let us first create a table −mysql> create table DemoTable1948    (    StudentCode varchar(20)    ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1948 values('121John_567'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1948 values('Adam_101'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1948 values('Bob_563'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1948 values('Sam_346'); Query OK, 1 row affected (0.00 sec)Display all records from the table using select statement −mysql> ... Read More

Let us first create a table −mysql> create table DemoTable1947    (    Id int,    Name varchar(20)    ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1947 values(101, 'Chris'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1947 values(102, 'David'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1947 values(103, 'Mike'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1947 values(104, 'Bob'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1947 values(105, 'Sam'); Query OK, 1 row affected (0.00 sec)Display ... Read More

Let us first create a table −mysql> create table DemoTable1946    (    ShippingDate date    ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1946 values('2019-12-11'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1946 values('2018-12-11'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1946 values('2017-12-11'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1946 values('2019-04-22'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1946 values('2019-12-11'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1946 values('2015-12-11'); Query OK, 1 ... Read More

To insert records from multiple tables, use INSERT INTO SELECT statement. Here, we will insert records from 2 tables.Let us first create a table −mysql> create table DemoTable1943    (    Name varchar(20)    ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1943 values('Chris'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1943 values('Robert'); Query OK, 1 row affected (0.00 sec)Display all records from the table using select statement −mysql> select * from DemoTable1943;This will produce the following output −+--------+ | Name   | +--------+ | Chris ... Read More

For this, use regular expression. The syntax is as follows −select * from information_schema.schemata WHERE SCHEMA_NAME REGEXP '^yourValue_+[A-Z]';Let us create some databases −mysql> create database bank_APP1; Query OK, 1 row affected (0.00 sec) mysql> create database bank_APP2; Query OK, 1 row affected (0.00 sec) mysql> create database bank_APP3; Query OK, 1 row affected (0.00 sec)Here is the query to get all databases having upper case character after some word −mysql> select * from information_schema.schemata    WHERE SCHEMA_NAME REGEXP '^bank_+[A-Z]';This will produce the following output −+--------------+-------------+----------------------------+------------------------+----------+ | CATALOG_NAME | SCHEMA_NAME | DEFAULT_CHARACTER_SET_NAME | DEFAULT_COLLATION_NAME | SQL_PATH | +--------------+-------------+----------------------------+------------------------+----------+ | def   ... Read More

For this, use COUNT(*) along with GROUP BY clause. Let us first create a table −mysql> create table DemoTable1942    (    Value int    ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1942 values(1); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1942 values(2); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1942 values(3); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1942 values(2); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1942 values(3); Query OK, 1 row affected (0.00 ... Read More

To return the field with highest count, use ORDER BY COUNT(*). Let us first create a table −mysql> create table DemoTable1940    (    FirstName varchar(20)    ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1940 values('Chris'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1940 values('Mike'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1940 values('Adam'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1940 values('Mike'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1940 values('Chris'); Query OK, 1 row ... Read More

For this, you can use LEFT(). Let us first create a table −mysql> create table DemoTable1939    (    FullName varchar(20)    ); Query OK, 0 rows affected (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1939 values('Adam Smith'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1939 values('Robert Downey, Jr.'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1939 values('Sylvester Stallone'); Query OK, 1 row affected (0.00 sec) mysql> insert into DemoTable1939 values('Chris Hemsworth'); Query OK, 1 row affected (0.00 sec)Display all records from the table using select statement −mysql> ... Read More

To display all fields, set the database with table_schema and specific table with table_name as in the below syntax −select column_name as anyAliasName from information_schema.columns    where table_schema=database()    and table_name=’yourTableName’\GLet us first create a table −mysql> create table DemoTable1938    (    StudentId int,    StudentName varchar(20),    StudentAge int,    StudentCountryName varchar(20),    StudentMobileNumber bigint    ); Query OK, 0 rows affected (0.00 sec)Here is the query to display all fields of a table −mysql> select column_name as ALL_FIELDS from information_schema.columns    where table_schema=database()    and table_name='DemoTable1938'\GThis will produce the following output −*************************** 1. row *************************** ALL_FIELDS: StudentId ... Read More