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MySQL Articles
Page 287 of 355
How to convert positive value to negative while inserting in MySQL?
Let us first create a tablemysql> create table recordsDemo -> ( -> UserId int, -> Value int -> ); Query OK, 0 rows affected (0.52 sec)Now insert some records in the table using insert command.The query is as followsmysql> insert into recordsDemo values(1, 10); Query OK, 1 row affected (0.17 sec) mysql> insert into recordsDemo values(3, 598); Query OK, 1 row affected (0.18 sec) mysql> insert into recordsDemo values(5, 786); Query OK, 1 row affected (0.25 sec) mysql> insert into recordsDemo values(7, 189); Query OK, 1 row affected (0.16 sec) mysql> insert into recordsDemo values(9, 345); ...
Read MoreStored procedure using variable in LIMIT expression?
Let us firs create a tablemysql> create table LimitWithStoredProcedure -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Name varchar(10) -> ); Query OK, 0 rows affected (0.47 sec)Insert some records in the table using insert command.The query is as followsmysql> insert into LimitWithStoredProcedure(Name) values('John'); Query OK, 1 row affected (0.15 sec) mysql> insert into LimitWithStoredProcedure(Name) values('Chris'); Query OK, 1 row affected (0.15 sec) mysql> insert into LimitWithStoredProcedure(Name) values('Maxwell'); Query OK, 1 row affected (0.28 sec) mysql> insert into LimitWithStoredProcedure(Name) values('Bob'); Query OK, 1 row affected (0.24 sec) mysql> insert into LimitWithStoredProcedure(Name) values('David'); Query ...
Read MoreHow to revert rows to default column value in MySQL?
To revert rows to default column value, let us first create a demo tablemysql> create table defaultDemo -> ( -> Id int -> ); Query OK, 0 rows affected (0.48 sec)Insert some records in the table using insert command.The query is as followsmysql> insert into defaultDemo values(10); Query OK, 1 row affected (0.25 sec) mysql> insert into defaultDemo values(20); Query OK, 1 row affected (0.13 sec) mysql> insert into defaultDemo values(30); Query OK, 1 row affected (0.14 sec) mysql> insert into defaultDemo values(40); Query OK, 1 row affected (0.11 sec) mysql> insert into defaultDemo values(80); Query OK, ...
Read MoreResolve the error Column count doesn't match value count in MySQL?
This type of error occurs when number of columns does not match whenever you are inserting records in the destination table. For a demo example, let us create a tablemysql> create table errorDemo -> ( -> User_Id int NOT NULL AUTO_INCREMENT, -> User_Name varchar(20), -> PRIMARY KEY(User_Id) -> ); Query OK, 0 rows affected (0.47 sec)The error is as followsmysql> insert into errorDemo values('John'); ERROR 1136 (21S01): Column count doesn't match value count at row 1To avoid this type of error, you need to use the following syntaxinsert into yourTableName(yourColumnName1, yourColumnName2, ...N)values(yourValue1, yourValue2, ....N);Insert some ...
Read MoreGet MySQL maximum value from 3 different columns?
To get the maximum value from three different columns, use the GREATEST() function.The syntax is as followsSELECT GREATEST(yourColumnName1, yourColumnName2, yourColumnName3) AS anyAliasName FROM yourTableName;To understand the above syntax, let us create a table. The query to create a table is as followsmysql> create table MaxOfThreeColumnsDemo -> ( -> First int, -> Second int, -> Third int -> ); Query OK, 0 rows affected (0.73 sec)Insert some records in the table using insert command.The query is as followsmysql> insert into MaxOfThreeColumnsDemo values(30, 90, 60); Query OK, 1 row affected (0.16 sec) mysql> insert into MaxOfThreeColumnsDemo values(100, ...
Read MoreHow to alter a MySQL Column from varchar(30) to varchar(100)?
You need to use ALTER TABLE command along with MODIFYThe syntax is as followsALTER TABLE yourTableName MODIFY COLUMN yourColumnName varchar(100) NOT NULL;To understand the above syntax, let us create a table. The query to create a table is as followsmysql> create table syntaxOfAlterCommandDemo -> ( -> UserId int, -> UserName varchar(30), -> UserAge int, -> UserCityName varchar(50) -> ); Query OK, 0 rows affected (0.51 sec)Let us check the description of the table.The query is as followsmysql> desc syntaxOfAlterCommandDemo;The following is the output+--------------+-------------+------+-----+---------+-------+ | Field | Type ...
Read MoreHow to add +1 to existing MySQL values?
Let us see an example and create a table first.mysql> create table Add1ToExistingValue -> ( -> Value int -> ); Query OK, 0 rows affected (0.56 sec)Insert some records in the table using insert command.The query is as followsmysql> insert into Add1ToExistingValue values(10); Query OK, 1 row affected (0.12 sec) mysql> insert into Add1ToExistingValue values(13); Query OK, 1 row affected (0.15 sec) mysql> insert into Add1ToExistingValue values(15); Query OK, 1 row affected (0.13 sec) mysql> insert into Add1ToExistingValue values(16); Query OK, 1 row affected (0.14 sec) mysql> insert into Add1ToExistingValue values(20); Query OK, 1 row affected (0.16 sec) mysql> insert into Add1ToExistingValue values(40); Query OK, 1 row affected (0.15 sec) mysql> insert into Add1ToExistingValue values(50); Query OK, 1 row affected (0.11 sec) mysql> insert into Add1ToExistingValue values(55); Query OK, 1 row affected (0.17 sec) mysql> insert into Add1ToExistingValue values(56); Query OK, 1 row affected (0.17 sec)Display all records from the table using select statement.The query is as followsmysql> select *from Add1ToExistingValue;The following is the output+-------+ | Value | +-------+ | 10 ...
Read MoreMySQL replace values in a table?
To replace values in a table, use the CASE statement. To understand the concept, let us create a table. The query to create a table is as followsmysql> create table replaceValueDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Name varchar(10), -> isGreaterThan18 varchar(10) -> ); Query OK, 0 rows affected (0.49 sec)Insert some records in the table using insert command.The query is as followsmysql> insert into replaceValueDemo(Name, isGreaterThan18) values('John', 'YES'); Query OK, 1 row affected (0.24 sec) mysql> insert into replaceValueDemo(Name, isGreaterThan18) values('Carol', 'NO'); Query OK, 1 row affected (0.16 sec) ...
Read MoreGet the second last row of a table in MySQL?
You need to use ORDER BY clause to get the second last row of a table in MySQL.The syntax is as follows.select *from yourTableName order by yourColumnName DESC LIMIT 1, 1;To understand the above syntax, let us create a table. The query to create a table is as follows.mysql> create table secondLastDemo -> ( -> StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> StudentName varchar(10) -> ); 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 secondLastDemo(StudentName) values('Larry'); Query OK, 1 row affected (0.15 ...
Read MoreHow to SELECT all values from a table only once if they're duplicated?
You can use distinct keyword to select all values from a table only once if they are repeated.The syntax is as followsselect distinct yourColumnName from yourTableName;To understand the above syntax, let us create a table. The query to create a table is as follows.mysql> create table displayOnlyDistinctValue -> ( -> UserId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> UserName varchar(100), -> UserAge int -> ); 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 displayOnlyDistinctValue(UserName, UserAge) values('Larry', 23); Query OK, 1 row affected ...
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