To understand the concept, let us first create a demo table.mysql> create table addToExistingValueDemo    -> (    -> Instructor_Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,    -> Instructor_Name varchar(30),    -> Instructor_TechnicalSubject text    -> ); Query OK, 0 rows affected (0.54 sec)Insert some records in the table using insert command. The query is as follows −mysql> insert into addToExistingValueDemo(Instructor_Name, Instructor_TechnicalSubject) values('John', 'C, C++'); Query OK, 1 row affected (0.15 sec) mysql> insert into addToExistingValueDemo(Instructor_Name, Instructor_TechnicalSubject) values('Carol', 'Java, Python'); Query OK, 1 row affected (0.18 sec) mysql> insert into addToExistingValueDemo(Instructor_Name, Instructor_TechnicalSubject) values('Bob', 'MySQL, SQL Server'); Query OK, 1 row ... Read More

To count boolean field values within a single query, you can use CASE statement. Let us create a demo table for our example −mysql> create table countBooleanFieldDemo    -> (    -> StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY,    -> StudentFirstName varchar(20),    -> isPassed tinyint(1)    -> ); Query OK, 0 rows affected (0.63 sec)Insert some records in the table using insert command. The query is as follows −mysql> insert into countBooleanFieldDemo(StudentFirstName, isPassed) values('Larry', 0); Query OK, 1 row affected (0.12 sec) mysql> insert into countBooleanFieldDemo(StudentFirstName, isPassed) values('Mike', 1); Query OK, 1 row affected (0.17 sec) mysql> insert into ... Read More

To avoid inserting duplicate rows in MySQL, you can use UNIQUE(). The syntax is as follows −ALTER TABLE yourTableName ADD UNIQUE(yourColumnName1, yourColumnName2, ...N);To understand the above syntax, let us create a table. The query to create a table is as follows −mysql> create table avoidInsertingDuplicateRows    -> (    -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,    -> FirstValue int,    -> SecondValue int    -> ); Query OK, 0 rows affected (0.53 sec)Now check the description of table using desc command. The query is as follows −mysql> desc avoidInsertingDuplicateRows;Sample The following is The output −+-------------+---------+------+-----+---------+----------------+ | Field       ... Read More

The desc is a MySQL reserved word, therefore you cannot use it. But, if you still want to set the column name as ‘desc’, you need to use backticks. The backtick notation is (` `).To understand the above concept, let us create a table. The query to create a table is as follows −mysql> create table useOfDescColumnNameDemo    -> (    -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,    -> Name varchar(20),    -> `desc` varchar(200) default 'GOOD'    -> ); Query OK, 0 rows affected (0.60 sec)Insert some records in the table using insert command. The query is as follows ... Read More

To create a view only if it does not already exist, you can use the following syntax −CREATE OR REPLACE VIEW yourViewName AS SELECT *FROM yourTableName;To understand the above syntax, let us create a table. The query to create a table is as follows −mysql> create table createViewDemo    -> (    -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,    -> Name varchar(20)    -> ); Query OK, 0 rows affected (0.58 sec)Insert some records in the table using insert command. The query is as follows −mysql> insert into createViewDemo(Name) values('John'); Query OK, 1 row affected (0.22 sec) mysql> insert into ... Read More

The syntax is as follows to count all characters in all rows of a field −select sum(char_length(yourColumnName)) AS anyAliasName from yourTableName;To understand the above syntax, let us create a table. The query to create a table is as follows −mysql> create table CountAllCharactersDemo    -> (    -> UserId int NOT NULL AUTO_INCREMENT PRIMARY KEY,    -> UserName varchar(20),    -> UserSubject text    -> ); Query OK, 0 rows affected (0.47 sec)Insert some records in the table using insert command. The query is as follows −mysql> insert into CountAllCharactersDemo(UserName, UserSubject) values('Larry', 'Introduction To Java'); Query OK, 1 row affected (0.19 ... Read More

The syntax is as follows to trim commas −SELECT TRIM(BOTH ', ' FROM yourColumnName) from yourTableName;Let us see an example −mysql> create table TrimCommasDemo    -> (    -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,    -> AllTechnicalSkills text    -> ); Query OK, 0 rows affected (0.81 sec)Now you can insert some records in the table using insert command. The query is as follows −mysql> insert into TrimCommasDemo(AllTechnicalSkills) values(', C, C++, Java, '); Query OK, 1 row affected (0.14 sec) mysql> insert into TrimCommasDemo(AllTechnicalSkills) values(', MySQL, SQL Server, MongoDB, '); Query OK, 1 row affected (0.13 sec) mysql> ... Read More

You can use CASE statement for this. Let us see an example −mysql> create table BooleanEvaluationDemo    -> (    -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,    -> FirstValue int,    -> SecondValue int    -> ); Query OK, 0 rows affected (0.71 sec)Insert some records in the table using insert command. The query is as follows −mysql> insert into BooleanEvaluationDemo(FirstValue, SecondValue) values(10, 5); Query OK, 1 row affected (0.20 sec) mysql> insert into BooleanEvaluationDemo(FirstValue, SecondValue) values(15, 20); Query OK, 1 row affected (0.16 sec) mysql> insert into BooleanEvaluationDemo(FirstValue, SecondValue) values(50, 40); Query OK, 1 row affected (0.14 ... Read More

The syntax is as follows to skip the duplicate value and select only one from the duplicated values −select min(yourColumnName1), yourColumnName2 from yourTableName group by yourColumnName2;To understand the above syntax, let us create a table. The query to create a table is as follows −mysql> create table doNotSelectDuplicateValuesDemo    -> (    -> User_Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,    -> User_Name varchar(20)    -> ); Query OK, 0 rows affected (0.78 sec)Now you can insert some records in the table using insert command. The query is as follows −mysql> insert into doNotSelectDuplicateValuesDemo(User_Name) values('John'); Query OK, 1 row affected ... Read More

You can use IN operator for this.The syntax is as follows −SELECT *FROM yourTableName WHERE yourColumnName IN(‘yourValue1’, ‘yourValue2’, ‘yourValue3’, ...........N);To understand the above syntax, let us create a table. The query to create a table is as follows −mysql> create table InOperatorDemo    -> (    -> ClientId int    -> ); Query OK, 0 rows affected (0.52 sec)Insert some records in the table using insert command. The query is as follows −mysql> insert into InOperatorDemo values(101); Query OK, 1 row affected (0.19 sec) mysql> insert into InOperatorDemo values(110); Query OK, 1 row affected (0.11 sec) mysql> insert into InOperatorDemo ... Read More