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MySQL Articles
Page 254 of 355
Counting presence of a NOT NULL value in MySQL
To count presence of a NOT NULL value, use aggregate function COUNT(yourColumnName). Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, NumberOfQuestion int, NumberOfSolution int ); Query OK, 0 rows affected (0.20 sec)Insert some records in the table using insert command. Here, some of the values are NULL −mysql> insert into DemoTable(NumberOfQuestion, NumberOfSolution) values(20, 10); Query OK, 1 row affected (0.06 sec) mysql> insert into DemoTable(NumberOfQuestion, NumberOfSolution) values(20, 2); Query OK, 1 row affected (0.04 sec) mysql> insert into DemoTable(NumberOfQuestion, NumberOfSolution) values(20, NULL); Query ...
Read MoreCounting common elements in MySQL?
To count common elements, use COUNT() and GROUP BY. Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, Number int ); Query OK, 0 rows affected (0.20 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(Number) values(10); Query OK, 1 row affected (0.06 sec) mysql> insert into DemoTable(Number) values(20); Query OK, 1 row affected (0.04 sec) mysql> insert into DemoTable(Number) values(20); Query OK, 1 row affected (0.04 sec) mysql> insert into DemoTable(Number) values(30); Query OK, 1 row affected (0.04 sec) ...
Read MoreMySQL Stored Procedure to create a table?
Following is the query to create a stored procedure that creates a table. Here, we are creating a table with three columns, one of them is Id −mysql> DELIMITER // mysql> CREATE PROCEDURE Stored_Procedure_CreatingTable() BEGIN create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, UserFirstName varchar(20), UserLastName varchar(20) ); END; // Query OK, 0 rows affected (0.16 sec) mysql> DELIMITER ;Now you can call stored procedure with the help of CALL command −mysql> call Stored_Procedure_CreatingTable(); ...
Read MoreLower case column names with MySQL SELECT?
Let us first create a table −mysql> create table DemoTable ( UserId int NOT NULL AUTO_INCREMENT PRIMARY KEY, UserFirstName varchar(20), UserLastName varchar(20), UserAge int, UserCountryName varchar(20) ); Query OK, 0 rows affected (0.27 sec)Now check the description of table.mysql> desc DemoTable;This will produce the following output −+-----------------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+-------------+------+-----+---------+----------------+ | UserId | int(11) | NO | PRI ...
Read MoreMySQL Select when a grouped record has multiple matching strings?
You can use regular expression for this. Let us first create a table −mysql> create table DemoTable ( ProductId int NOT NULL AUTO_INCREMENT PRIMARY KEY, ProductName varchar(20) ); Query OK, 0 rows affected (0.19 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(ProductName) values('Product-1'); Query OK, 1 row affected (0.05 sec) mysql> insert into DemoTable(ProductName) values('Product2'); Query OK, 1 row affected (0.06 sec) mysql> insert into DemoTable(ProductName) values('Product1'); Query OK, 1 row affected (0.04 sec) mysql> insert into DemoTable(ProductName) values('Product-3'); Query OK, 1 row affected (0.05 sec) mysql> ...
Read MoreHow can I find all columns where the column name length is greater than 5 in MySQL?
Use HAVING to find all columns where the column name length is greater than 5. This will produce the following output −+-------------------+-------------------------+ | TABLE_NAME | COLUMN_NAME | +-------------------+-------------------------+ | DemoTable | UserId | | DemoTable | EndDate | | DemoTable | StartDate | | DemoTable | StudentFavouriteSubject | | DemoTable ...
Read MoreHow can I calculate the total value of products from my MySQL product table?
Let us first create a table −mysql> create table DemoTable ( ProductId int NOT NULL AUTO_INCREMENT PRIMARY KEY, ProductQuantity int, ProductPrice int ); Query OK, 0 rows affected (0.19 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(ProductQuantity, ProductPrice) values(10, 100); Query OK, 1 row affected (0.06 sec) mysql> insert into DemoTable(ProductQuantity, ProductPrice) values(5, 11); Query OK, 1 row affected (0.04 sec) mysql> insert into DemoTable(ProductQuantity, ProductPrice) values(3, 140); Query OK, 1 row affected (0.05 sec) mysql> insert into DemoTable(ProductQuantity, ProductPrice) values(2, 450); Query OK, 1 row affected ...
Read MoreHow can I avoid “repair with keycache” in MySQL?
To avoid repair with keycache in MySQL, you need to follow the below syntax −create table yourNewTableName as (select *from yourOldTableName); alter table yourNewTableName add index(yourCoumnName);Let us first create a table −mysql> create table DemoTable ( StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, StudentFirstName varchar(20), StudentLastName varchar(20) ); Query OK, 0 rows affected (0.24 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(StudentFirstName, StudentLastName) values('John', 'Doe'); Query OK, 1 row affected (0.05 sec) mysql> insert into DemoTable(StudentFirstName, StudentLastName) values('David', 'Miller'); Query OK, 1 row affected (0.05 sec)Display all records from ...
Read MoreFetch data between two rows in MySQL?
To fetch data between two rows, use the concept of LIMIT. Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, Name varchar(10) ); Query OK, 0 rows affected (0.22 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(Name) values('Larry'); Query OK, 1 row affected (0.06 sec) mysql> insert into DemoTable(Name) values('Robert'); Query OK, 1 row affected (0.05 sec) mysql> insert into DemoTable(Name) values('Chris'); Query OK, 1 row affected (0.05 sec) mysql> insert into DemoTable(Name) values('David'); Query OK, 1 row affected ...
Read MoreMySQL filtering by multiple columns?
To perform filtering by multiple columns, use where clause along with OR. Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, Name varchar(10), Score int ); Query OK, 0 rows affected (0.28 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(Name, Score) values('John', 80); Query OK, 1 row affected (0.04 sec) mysql> insert into DemoTable(Name, Score) values('John', 90); Query OK, 1 row affected (0.06 sec) mysql> insert into DemoTable(Name, Score) values('Carol', 89); Query OK, 1 row affected (0.04 sec) ...
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