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MySQLi Articles
Page 276 of 341
Using MySQL SELECT for simple BOOLEAN evaluation?
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 MoreHow to trim commas with MySQL?
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 MoreHow to count all characters in all rows of a field in MySQL?
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 MoreMySQL add “prefix” to every column?
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 MoreWhy can't we use column name “desc” in MySQL?
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 MoreHow to avoid inserting duplicate rows in MySQL?
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 MoreCount boolean field values within a single MySQL query?
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 MoreMySQL query to discover current default database collation (via command line client)?
You need to use INFORMATION_SCHEMA.SCHEMATA for current default database collation.The syntax is as followsSELECT DEFAULT_COLLATION_NAME FROM information_schema.SCHEMATA WHERE SCHEMA_NAME = 'yourDatabaseName' LIMIT 1;Let us implement the above syntax to discover current default database collation (via command line client). Our database here is ‘sample’.The query is as follows −mysql> SELECT DEFAULT_COLLATION_NAME FROM information_schema.SCHEMATA WHERE SCHEMA_NAME = 'sample' LIMIT 1;The following is the output+------------------------+ | DEFAULT_COLLATION_NAME | +------------------------+ | utf8_general_ci | +------------------------+ 1 row in set (0.00 sec)
Read MoreAdd to existing value in MySQL column using CONCAT function?
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 MoreWhy does MySQL refuse pipe ('|') character in string on INSERT INTO?
To insert pipe(|) character in string on INSERT INTO, let us first see an example and create a table. The query to create a table is as followsmysql> create table PipeInsertDemo -> ( -> UserId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> UserPassword varchar(100) -> ); 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 PipeInsertDemo(UserPassword) values('John123|'); Query OK, 1 row affected (0.15 sec) mysql> insert into PipeInsertDemo(UserPassword) values('|123456CarolTaylor'); Query OK, 1 row affected ...
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