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MySQLi Articles
Page 237 of 341
MySQL query to count frequency of students with the same age?
You can use COUNT(*) along with GROUP BY for this. Let us first create a table −mysql> create table DemoTable ( StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, StudentAge int ); Query OK, 0 rows affected (0.59 sec)Insert records in the table using insert command −mysql> insert into DemoTable(StudentAge) values(16); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable(StudentAge) values(17); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable(StudentAge) values(18); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable(StudentAge) values(17); Query OK, 1 row affected (0.13 sec) mysql> insert into ...
Read MoreHow to update all dates in a Table?
You can use UPDATE with DATE_ADD() to update all dates. Let us first create a table −mysql> create table DemoTable ( ClientId int NOT NULL AUTO_INCREMENT PRIMARY KEY, ClientProjectDueDate date ); Query OK, 0 rows affected (1.19 sec)Insert records in the table using insert command −mysql> insert into DemoTable(ClientProjectDueDate) values('2018-01-21'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable(ClientProjectDueDate) values('2019-03-25'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable(ClientProjectDueDate) values('2013-11-01'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable(ClientProjectDueDate) values('2015-06-14'); Query OK, 1 row affected (0.23 sec)Display all records from ...
Read MoreHow can I modify an existing column's data type?
To modify an existing column’s data type, you can use MODIFY. Let us first create a table −mysql> create table DemoTable ( ClientId varchar(100), ClientName varchar(100), ClientAge int, ClientProjectDeadline timestamp, ClientCountryName varchar(100), isMarried boolean, ClientNumber bigint ); Query OK, 0 rows affected (0.70 sec)Check the description of table −mysql> desc DemoTable;This will produce the following output −+-----------------------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-----------------------+--------------+------+-----+---------+-------+ | ClientId ...
Read MoreGet MAX and MIN values along with their row id in MySQL?
You can use aggregate function MAX() and MIN() for this.Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, Number1 int, Number2 int ); Query OK, 0 rows affected (0.89 sec)Insert records in the table using insert command −mysql> insert into DemoTable(Number1, Number2) values(67, 45); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable(Number1, Number2) values(90, 40); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable(Number1, Number2) values(80, 43); Query OK, 1 row affected (0.48 sec)Display all records from the table using select ...
Read MoreHow to concatenate all columns in MySQL?
First, you need to know how many columns are present in a table. Following is the syntax to know the column names −show columns from yourTableName;Following is the syntax to concatenate all columns −select concat(yourColumnName1, yourColumnName2, yourColumnName3, ........N) from yourTableName;Let us first create a table −mysql> create table DemoTable ( CustomerId int, CustomerName varchar(20), CustomerAge int ); Query OK, 0 rows affected (0.66 sec)Following is the query to know the exact column −mysql> show columns from DemoTable;This will produce the following output −+--------------+-------------+------+-----+---------+-------+ | Field | Type | Null ...
Read MoreProblem using the column name 'from' in a MySQL query?
You cannot use ‘from’ as column name directly because ‘from’ is a reserved word in MySQL.If you want to still use it, then you need to use the backtick symbol.Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, `from` varchar(100), Name varchar(10) ); Query OK, 0 rows affected (0.92 sec)Insert records in the table using insert command −mysql> insert into DemoTable(`from`, Name) values('US', 'John'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable(`from`, Name) values('UK', 'Carol'); Query OK, 1 row affected (0.14 sec) mysql> ...
Read MoreHow to get the primary key "column name" of a specific table in MySQL?
Let us first create a table wherein we have a Primary Key CustomerId −mysql> create table DemoTable ( CustomerId int NOT NULL AUTO_INCREMENT, CustomerName varchar(20), CustomerAge int, CustomerCountryName varchar(100), PRIMARY KEY(CustomerId) ); Query OK, 0 rows affected (0.94 sec)Following is the query to get the primary key “column name” of a specific table in MySQL −mysql> SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE WHERE TABLE_NAME = 'DemoTable' AND CONSTRAINT_NAME = 'PRIMARY';This will produce the following output −+-------------+ | COLUMN_NAME | +-------------+ | CustomerId | +-------------+ 1 row in set, 2 warnings (0.12 sec)
Read MoreWhat is the equivalent of EXCEPT in MySQL?
You cannot use EXCEPT in MySQL, instead use the NOT IN operator. Let us first create a table −mysql> create table DemoTable ( Number1 int ); Query OK, 0 rows affected (0.71 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(100); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values(200); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values(300); Query OK, 1 row affected (0.13 sec)Display all records from the table using select statement −mysql> select * from DemoTable;This will produce the following output −+---------+ | ...
Read MoreWhy I am facing a problem using the field 'from' in SQL query?
You cannot use from as a column name directly because from is a reserved word in MySQL. To avoid this, you need to use backtick symbol. Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, `from` varchar(100), Name varchar(10) ); Query OK, 0 rows affected (0.92 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(`from`, Name) values('US', 'John'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable(`from`, Name) values('UK', 'Carol'); Query OK, 1 row affected (0.14 sec) mysql> ...
Read MoreExcept not working in MySQL?
You cannot use except in MySQL. You can work with NOT IN operator to get the same result. Let us first create a table −mysql> create table DemoTable1 ( Number1 int ); Query OK, 0 rows affected (0.71 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1 values(100); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable1 values(200); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable1 values(300); Query OK, 1 row affected (0.13 sec)Display all records from the table using select statement:mysql> select *from DemoTable1This will produce the following output −+---------+ | Number1 | +---------+ | 100 | | 200 | | 300 | +---------+ 3 rows in set (0.00 sec)Following ...
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