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MySQL Articles
Page 299 of 355
How to delete all rows except some in MySQL?
You can use NOT IN operator for the rows you do not want to delete. Following is the syntax −delete from yourTableName where yourColumnName NOT IN(‘yourValue1’, ‘yourValue2’, ‘yourValue3’, .........N);Let us first create a table −mysql> create table deleteAllRowsWithCondition -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Name varchar(20) -> ); Query OK, 0 rows affected (0.84 sec)Following is the query to insert some records in the table using insert command −mysql> insert into deleteAllRowsWithCondition(Name) values('Larry'); Query OK, 1 row affected (0.14 sec) mysql> insert into deleteAllRowsWithCondition(Name) values('John'); Query OK, 1 row affected ...
Read MoreHow to find if a column is auto_increment in MySQL?
To find if a column is auto_increment in MySQL, you can use the following syntax −select COLUMN_NAME from information_schema.columns where TABLE_SCHEMA='yourDatabaseName' and TABLE_NAME='yourTableName' and EXTRA like '%auto_increment%';Let us first create a table. Here, ClientId is set AUTO_INCREMENT −mysql> create table autoIncrementTableDemo -> ( -> ClientId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> ClientName varchar(20), -> ClientAge int, -> ClientAddress varchar(100), -> ClientCountryName varchar(100) -> ); Query OK, 0 rows affected (0.61 sec)Now, let us find whether any of the column is auto_increment −mysql> select COLUMN_NAME from information_schema.columns where TABLE_SCHEMA='test' and TABLE_NAME='autoIncrementTableDemo' and EXTRA ...
Read MoreMySQL query to find sum of fields with same column value?
Use GROUP BY clause for this. Let us first create a table −mysql> create table sumOfFieldsDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> ClientSerialNumber varchar(100), -> ClientCost int -> ); Query OK, 0 rows affected (0.50 sec)Following is the query to insert some records in the table using insert command −mysql> insert into sumOfFieldsDemo(ClientSerialNumber, ClientCost) values('1111', 450); Query OK, 1 row affected (0.16 sec) mysql> insert into sumOfFieldsDemo(ClientSerialNumber, ClientCost) values('2222', 550); Query OK, 1 row affected (0.15 sec) mysql> insert into sumOfFieldsDemo(ClientSerialNumber, ClientCost) values('3333', 150); Query OK, 1 row affected (0.64 ...
Read MoreUpdate multiple rows in a single column in MySQL?
To update multiple rows in a single column, use CASE statement. Let us first create a table −mysql> create table updateMultipleRowsDemo -> ( -> StudentId int, -> StudentMathScore int -> ); Query OK, 0 rows affected (0.63 sec)Following is the query to insert records in the table using insert command −mysql> insert into updateMultipleRowsDemo values(10001, 67); Query OK, 1 row affected (0.14 sec) mysql> insert into updateMultipleRowsDemo values(10002, 69); Query OK, 1 row affected (0.15 sec) mysql> insert into updateMultipleRowsDemo values(10003, 89); Query OK, 1 row affected (0.14 sec) mysql> insert into updateMultipleRowsDemo values(10004, 99); Query ...
Read MoreHow to sort more than one column at a time in MySQL?
To sort more than one column at a time, you can use ORDER BY clause. Following is the syntax −select yourColumnName1, yourColumnName2, yourColumnName3 from yourTableName order by yourColumnName2, yourColumnName3;Let us first create a table −mysql> create table doubleSortDemo -> ( -> StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> StudentName varchar(100), -> StudentCountryName varchar(10) -> ); Query OK, 0 rows affected (0.71 sec)Following is the query to insert records in the table using insert command −mysql> insert into doubleSortDemo(StudentName, StudentCountryName) values('John', 'AUS'); Query OK, 1 row affected (0.21 sec) mysql> insert into doubleSortDemo(StudentName, StudentCountryName) values('Sam', ...
Read MoreMySQL query to display all the fields that contain a capital letter?
To display all the fields that contain a capital letter, use the RLIKE that performs a pattern match of a string expression against a pattern.Let us first create a table −mysql> create table contains_capital_letterDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Name varchar(100) -> ); Query OK, 0 rows affected (1.42 sec)Following is the query to insert some records in the table using insert command −mysql> insert into contains_capital_letterDemo(Name) values('Larry'); Query OK, 1 row affected (0.17 sec) mysql> insert into contains_capital_letterDemo(Name) values('larry'); Query OK, 1 row affected (0.12 sec) mysql> ...
Read MoreMySQL search if more than one string contains special characters?
To search if strings contain special characters, you can use REGEXP. Following is the syntax −select * from yourTableName where yourColumnName REGEXP '[^a-zA-Z0-9]';Let us first create a table −mysql> create table specialCharactersDemo -> ( -> StudentId varchar(100) -> ); Query OK, 0 rows affected (0.58 sec)Insert records in the table using insert command. Following is the query −mysql> insert into specialCharactersDemo values('STU_1234'); Query OK, 1 row affected (0.15 sec) mysql> insert into specialCharactersDemo values('STU567'); Query OK, 1 row affected (0.14 sec) mysql> insert into specialCharactersDemo values('STU#1234'); Query OK, 1 row affected (0.13 sec) mysql> insert into specialCharactersDemo ...
Read MoreResolve MySQL ERROR 1064 (42000): You have an error in your syntax?
This error occurs if let’s say you used var_char instead of varchar type. To remove this type of error, use, for example, varchar(100) instead of var_char(100).Let us now see how this error occurs −mysql> create table removeErrorDemo -> ( -> StudentId int, -> StudentName var_char(50) -> );The following is the output displaying the error −ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'var_char(50) )' at line 4Now let us remove the error. Here is the query ...
Read MoreHow to select distinct value from one MySQL column only?
To select distinct value from one column only, you can use aggregate function MAX() along with GROUP BY. Let us first create a table −mysql> create table distinctFromOneColumn -> ( -> StudentId int, -> StudentName varchar(100) -> ); Query OK, 0 rows affected (0.77 sec)Following is the query to insert records in the table using insert command −mysql> insert into distinctFromOneColumn values(1001, 'John'); Query OK, 1 row affected (0.15 sec) mysql> insert into distinctFromOneColumn values(1002, 'Carol'); Query OK, 1 row affected (0.15 sec) mysql> insert into distinctFromOneColumn values(1001, 'Sam'); Query OK, 1 row affected ...
Read MoreHow to calculate value from multiple columns in MySQL?
To calculate a value from multiple columns, use GROUP BY. Following is the syntax −select yourColumnName1, sum(yourColumnName2*yourColumnName3) AS anyAliasName from yourTableName group by yourColumnName1;Let us first create a table −mysql> create table calculateValueDemo -> ( -> Id int, -> ProductPrice int, -> ProductWeight int -> ); Query OK, 0 rows affected (0.56 sec)Following is the query to insert records in the table using insert command −mysql> insert into calculateValueDemo values(100, 35, 5); Query OK, 1 row affected (0.16 sec) mysql> insert into calculateValueDemo values(101, 50, 3); Query OK, 1 row affected (0.16 sec) ...
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