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MySQLi Articles
Page 304 of 341
MySQL: selecting rows where a column is null?
To select rows where a column is null, you can use IS NULL from MySQL with the help of where clause.The syntax is as follows −select *from yourTableName where yourColumnName IS NULL;Let us first create a table to understand the concept −mysql> create table NULLDemo1 -> ( -> StudentId int, -> StudentName varchar(100) -> ); Query OK, 0 rows affected (1.48 sec)Inserting records into the table. The query to insert records is as follows −mysql> insert into NULLDemo1 values(NULL, 'John'); Query OK, 1 row affected (0.25 sec) mysql> ...
Read MoreWhat is the best way to display in Terminal a MySQL SELECT returning too many fields?
To achieve this, you can use the following syntax in MySQL −select *from yourTableName\G;Here, G can be used for vertical purpose. You need to add yourTableName.Let us create a table in order to understand the above syntax. Creating a table with the help of CREATE command.The following is the query to create a table −mysql> create table TooManyFieldsreturnDemo -> ( -> Id int, -> Name varchar(100), -> Age int -> ); Query OK, 0 rows affected (0.64 sec)Now you can insert records in the table ...
Read MoreHow to subtract 30 days from the current datetime in MySQL?
To subtract 30 days from current datetime, first we need to get the information about current date time, then use the now() method from MySQL. The now() gives the current date time.The method to be used for this is DATE_SUB() from MySQL. Here is the syntax to subtract 30 days from current datetime.The syntax is as follows −DATE_SUB(NOW(), INTERVAL 30 DAY);The above syntax calculates the current datetime first and in the next step, subtracts 30 days. Let us first seethe query to get the current datetime −mysql> select now();Here is the output −+---------------------+ | now() ...
Read MoreHow do I show a MySQL warning that just happened?
To show a MySQL warning, you can use the below syntax −SHOW WARNINGS;The above syntax only displays the immediate warning from MySQL prompt. Suppose you run another query between them or you have lost the MySQL connection, then SHOW WARNINGS will not work.Here is the query to display warnings −mysql> SHOW WARNINGS;Here is the output that displays immediate warning −+-------+------+---------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Level | Code | Message ...
Read MoreWhich rows are returned while using LIMIT with OFFSET in MySQL?
Suppose the LIMIT is 4 and OFFSET is 6 then it will return the rows from 7 to 10 i.e. will end with row 10. The LIMIT 4 and OFFSET 6 returns row 7, 8, 9, 10.You can understand the above concept by implementing LIMIT and OFFSET. Let us create a table.mysql> create table LimitOffsettable -> ( -> Id int -> ); Query OK, 0 rows affected (0.60 sec)Let us insert some records in the table. The query is as follows −Mysql> insert into LimitOffsettable values(1); Query OK, 1 row affected ...
Read MoreMySQL create user if it does not exist?
You can create user if it does not exist with the help of “create user” command. The command will work on MySQL version 5.7.6 and above. The syntax is as follows −mysql> CREATE USER IF NOT EXISTS 'yourUserName'@'localhost' IDENTIFIED BY 'yourPassword';Apply the above syntax to create a user if it does not exist. The query is as follows −mysql> CREATE USER IF NOT EXISTS 'Smith'@'localhost' IDENTIFIED BY 'Smith123456'; Query OK, 0 rows affected (0.29 sec)To check the new user is created or not, use the below query −mysql> SELECT User FROM mysql.user;The following is the output −+------------------+ | User ...
Read MoreHow to find MySQL my.cnf on my windows computer?
To find my.cnf on Windows system, first open the command prompt with the help of shortcut key Windows + R (run). The snapshot is as follows −Type “services.msc” on command prompt and press ENTER as shown in the following screenshot −Now, a new wizard will open. The snapshot is as follows −Now, search for MySQL. The snapshot is as follows −Right click on “MySQL80” and select “Properties” as in the following screenshot −As you can see in the above screenshot, “Path to executable” tells about the location of my.cnf on Windows.
Read MoreHow to part DATE and TIME from DATETIME in MySQL?
To part DATE and TIME from DATETIME, you can use the DATE_FORMAT() method from MySQL. The syntax is as follows −SELECT DATE_FORMAT(yourColumnName, '%Y-%m-%d') VariableName, DATE_FORMAT(yourColumnName, '%H:%i:%s') VariableName from yourTableName;To understand the above method DATE_FORMAT(), let us create a table with data type “datetime”.Creating a table −mysql> create table DateAndTimePartDemo -> ( -> YourDateandtime datetime -> ); Query OK, 0 rows affected (0.56 sec)Now, I am inserting current date and time using now(). The query is as follows −mysql> insert into DateAndTimePartDemo values(now()); Query OK, 1 row affected (0.37 sec)Display the record ...
Read MoreMySQL strip time component from datetime?
You can strip time component from datetime with the help of DATE() function. The syntax is as follows −SELECT DATE(yourColumnName) from yourTableName;To understand the above concept, let us first create a table −mysql> create table StripComponentDatetimeDemo -> ( -> YourDateTime datetime -> ); Query OK, 0 rows affected (0.60 sec)Let us now insert some records in the table. The query is as follows −mysql> insert into StripComponentDatetimeDemo values(date_add(now(), interval 1 day)); Query OK, 1 row affected (0.13 sec)Display records with the help of select statement. The query is as follows displaying ...
Read MoreBiggest value from two or more fields in MySQL?
To know the biggest value from two or more fields, use the function GREATEST() from MySQL.The syntax is as follows −SELECT GREATEST(MAX(yourColumnName1), MAX(yourColumnName2), ...............MAX(yourColumnName2) ) from yourTableName;Let us understand the above concept by creating a table with more than two columns −mysql> create table GreatestOfTwoOrMore -> ( -> Marks1 int, -> Marks2 int, -> Marks3 int -> ); Query OK, 0 rows affected (0.57 sec)Here is the query to insert records in a table −mysql> insert into GreatestOfTwoOrMore values(23, 78, 89); Query OK, 1 row ...
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