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MySQLi Articles
Page 36 of 341
System variables vs Local Variables in MySQL?
The local variable has the scope for only a set of statements or block of statement. Whenever a set of statements or block of statement has completed then local variable goes out of scope.For ExampleLocal variable can be used in stored procedure, function etc. It is used with the DECLARE keyword.The syntax is as follows to local variables.DECLARE yourVariableName dataType;The global variables or system variables has the scope across connections until server restart. It is set using GLOBAL keyword. The syntax is as follows −SET GLOBAL max_connections=value; OR SET @@global.max_connections=value;If you know port number then you can use system variable ...
Read MoreCan we use “IF NOT IN” in a MySQL procedure?
Let us first see the syntax of IF NOT IN in MySQL −if(yourVariableName NOT IN (yourValue1, yourValue2, ........N) ) then statement1 else statement2 endif Let us implement the above syntax to use IF NOT IN −mysql> DELIMITER // mysql> CREATE PROCEDURE IF_NOT_INDemo(IN value int) -> BEGIN -> if(value NOT IN (10, 20, 30) ) then -> select "Value Not Found"; -> else -> select "Value Found"; -> end if; -> END ...
Read MoreHow to place number 0 from a column at the end maintaining the ascending search order in MySQL?
Let us first create a table −mysql> create table DemoTable -> ( -> Number int -> ); Query OK, 0 rows affected (0.58 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(9); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values(4); Query OK, 1 row affected (0.31 sec) mysql> insert into DemoTable values(0); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values(7); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values(11); Query OK, 1 row affected (0.12 sec)Display all ...
Read MoreFix Error with TYPE=HEAP for temporary tables in MySQL?
The TYPE=HEAP deprecated in newer MySQL versions. You can use ENGINE=HEAP instead of TYPE. Following is the syntax −ENGINE=HEAP;Let us first create a table. Here, we have set Engine=HEAP −mysql> create TEMPORARY table DemoTable -> ( -> StudentId int, -> StudentName varchar(30) -> )Engine = HEAP; Query OK, 0 rows affected (0.00 sec)Let us check the definition of table −mysql> show create table DemoTable;OutputThis will produce the following output −+--------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Table | Create Table | +--------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | DemoTable | CREATE TEMPORARY TABLE `DemoTable` (`StudentId` int(11) DEFAULT NULL, `StudentName` varchar(30) COLLATE utf8_unicode_ci DEFAULT ...
Read MoreFinding number of occurrences of a specific string in MySQL?
Use LENGTH() for this. Let us first create a table −mysql> create table DemoTable -> ( -> Value text -> ); Query OK, 0 rows affected (0.74 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('10, 20, 10, 30, 10, 40, 50, 40'); Query OK, 1 row affected (0.24 sec)Display all records from the table using select statement −mysql> select *from DemoTable;OutputThis will produce the following output −+-------------------------+ | Value | +-------------------------+ | 10, 20, 10, 30, ...
Read MoreMySQL query to order by two fields and NULL values in chronological order?
Let us first create a table −mysql> create table DemoTable -> ( -> FirstName varchar(100), -> LastName varchar(100) -> ); Query OK, 0 rows affected (1.39 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('Sam', 'Brown'); Query OK, 1 row affected (0.25 sec) mysql> insert into DemoTable values(null, 'Smith'); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable values('David', 'Taylor'); Query OK, 1 row affected (0.22 sec) mysql> insert into DemoTable values('Mike', null); Query OK, 1 row affected (0.45 sec)Display all records from the table using select statement −mysql> select ...
Read MoreMySQL DATE_ADD() to increment a date based on the value in another column?
Let us first create a table with one of the columns as DueDate and another one “RepeatTime, which displays how many times, let’s say a user was reminded to submit the payment −mysql> create table DemoTable -> ( -> DueDate date, -> RepeatTime int -> ); Query OK, 0 rows affected (0.57 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('2019-01-23', 3); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values('2019-06-22', 6); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable values('2019-03-28', 2); Query ...
Read MoreChange a MySQL column to have NOT NULL constraint
To update the constraint, use the MODIFY command. Following is the syntax −alter table yourTableName modify yourExistingColumnName yourExistingDataType NOT NULL; Let us first create a table −mysql> create table DemoTable -> ( -> UserId int NOT NULL AUTO_INCREMENT, -> UserFirstName varchar(100), -> UserLastName varchar(100), -> UserEmailId varchar(100), -> UserPassword varchar(100), -> PRIMARY KEY(UserId) -> ); Query OK, 0 rows affected (0.91 sec)Following is the query to change the constraint of a column to NOT NULL −mysql> alter table DemoTable modify UserFirstName varchar(100) NOT NULL; Query OK, 0 rows affected (2.13 sec) Records: ...
Read MoreIs there a default ORDER BY value in MySQL?
There is no default ORDER BY value in MySQL. You need to specify ORDER BY clause explicitly. Following is the syntax −ORDER BY ASC; OR ORDER BY DESC;Let us first create a table −mysql> create table DemoTable -> ( -> StudentName varchar(100) -> ); Query OK, 0 rows affected (0.82 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('Sam'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable values('Chris'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values('David'); Query OK, 1 row affected (0.15 sec) ...
Read MoreGet the difference between dates and calculate salary with MySQL?
Let’s say you need to get the difference between dates (JoiningDate – EndDate) of a month i.e. days to calculate the salary. The daily-wage salary is let’s say 300; therefore for 20 days, it will 6000. In the same way, for 27 days, it will be 8100.For our example, let us first create a tablemysql> create table DemoTable -> ( -> JoinDate date, -> EndDate date -> , -> Value int -> ); Query OK, 0 rows affected (1.16 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('2019-01-01', '2019-01-31', ...
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