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MySQL Articles
Page 37 of 355
Difference Between MySql <> NULL and IS NOT NULL?
If you compare the operator with NULL value then you will get NULL value always and no result.Let us see some examples for comparison −mysql> select 10 NULL; +------------+ | 10 NULL | +------------+ | NULL | +------------+ 1 row in set (0.00 sec) mysql> select NULL NULL; +--------------+ | NULL NULL | +--------------+ | NULL | +--------------+ 1 row in set (0.00 sec) mysql> select 'Chris' NULL; +-----------------+ | 'Chris' NULL | +-----------------+ | NULL | +-----------------+ 1 row in ...
Read MoreDisplay MySQL histogram with negative values?
For negative values, use reverse() along with concat(). Let us first create a table −mysql> create table DemoTable632 ( histogramId int NOT NULL AUTO_INCREMENT PRIMARY KEY, histogramValue int, histogramImage text ); Query OK, 0 rows affected (0.78 sec)Insert some records in the table using insert command −mysql> insert into DemoTable632(histogramValue) values(2); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable632(histogramValue) values(3); Query OK, 1 row affected (0.34 sec) mysql> insert into DemoTable632(histogramValue) values(-6); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable632(histogramValue) values(-5); Query OK, 1 row affected (0.13 sec)Display all records from the table ...
Read MoreCount occurrences of known distinct values in MySQL
For this, you can use aggregate function SUM(). Let us first create a table −mysql> create table DemoTable636 ( StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, StudentFirstName varchar(100) ); Query OK, 0 rows affected (0.51 sec)Insert some records in the table using insert command −mysql> insert into DemoTable636(StudentFirstName) values('John'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable636(StudentFirstName) values('Robert'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable636(StudentFirstName) values('Robert'); Query OK, 1 row affected (0.22 sec) mysql> insert into DemoTable636(StudentFirstName) values('Sam'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable636(StudentFirstName) values('Mike'); Query OK, ...
Read MoreHow can I display all databases in MySQL and for each database show all tables?
For this, you can use INFORMATION_SCHEMA. Following is the syntax −select my_schema.SCHEMA_NAME, group_concat(tbl.TABLE_NAME) from information_schema.SCHEMATA my_schema left join information_schema.TABLES tbl on my_schema.SCHEMA_NAME=tbl.TABLE_SCHEMA group by my_schema.SCHEMA_NAME;Let us implement the above syntax in order to show all databases in MySQL and for each database −mysql> select my_schema.SCHEMA_NAME, group_concat(tbl.TABLE_NAME) from information_schema.SCHEMATA my_schema left join information_schema.TABLES tbl on my_schema.SCHEMA_NAME=tbl.TABLE_SCHEMA group by my_schema.SCHEMA_NAME;This will produce the following output −+---------------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | SCHEMA_NAME | group_concat(tbl.TABLE_NAME) ...
Read MoreComma separated argument applicable for IN operator in MySQL?
Use FIND_IN_SET() for command separated argument. Let us first create a table −mysql> create table DemoTable604 (Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, Title varchar(100)); Query OK, 0 rows affected (0.51 sec)Insert some records in the table using insert command −mysql> insert into DemoTable604(Title) values('MySQL'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable604(Title) values('C++'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable604(Title) values('MongoDB'); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable604(Title) values('Java'); Query OK, 1 row affected (0.14 sec)Display all records from the table using select statement −mysql> select *from DemoTable604;This ...
Read MorePurpose of using CHANGE command in MySQL?
The CHANGE command in MySQL is used to rename column name. Let us first create a table −mysql> create table DemoTable796 ( StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, Name varchar(100), StudentAge int ); Query OK, 0 rows affected (0.56 sec)Let us check the description of table −mysql> desc DemoTable796;This will produce the following output −+------------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------+--------------+------+-----+---------+----------------+ | StudentId | int(11) | NO | PRI | NULL | auto_increment | | Name ...
Read MoreHow to get the count of a specific value in a column with MySQL?
Let us first create a table −mysql> create table DemoTable ( Id int, Name varchar(100) ); Query OK, 0 rows affected (1.40 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(100, 'John'); Query OK, 1 row affected (0.44 sec) mysql> insert into DemoTable values(101, 'Chris'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable values(102, 'Chris'); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable values(103, 'Chris'); Query OK, 1 row affected (1.05 sec) mysql> insert into DemoTable values(104, 'David'); Query OK, 1 ...
Read MoreIs there any alternative for CONCAT() in MySQL?
Yes, an alternative is CONCAT_WS(). Let us first create a table −mysql> create table DemoTable ( StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, StudentName varchar(100) ); Query OK, 0 rows affected (0.74 sec)ExampleInsert some records in the table using insert command −mysql> insert into DemoTable(StudentName) values('Chris'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable(StudentName) values('Robert'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable(StudentName) values('Bob'); Query OK, 1 row affected (0.12 sec)Display all records from the table using select statement −mysql> select *from DemoTable;Output+-----------+-------------+ | StudentId | StudentName | +-----------+-------------+ | ...
Read MoreSelect query to display duplicate values with max date
For this, use GROUP BY and HAVING. Let us first create a table −mysql> create table DemoTable ( StudentName varchar(100), DueDate date ); Query OK, 0 rows affected (0.72 sec)ExampleInsert some records in the table using insert command −mysql> insert into DemoTable values('John', '2019-01-11'); Query OK, 1 row affected (0.26 sec) mysql> insert into DemoTable values('Chris', '2019-02-11'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable values('Chris', '2019-03-11'); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable values('John', '2019-04-11'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable values('Bob', '2019-05-11'); ...
Read MoreImplementing incremental search and display the values with a specific number in MySQL?
For this, you can use SUBSTRING_INDEX(). Let us first create a table −mysql> create table DemoTable (Number varchar(100)); Query OK, 0 rows affected (0.60 sec)ExampleInsert some records in the table using insert command −mysql> insert into DemoTable values('235678'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable values('1634990'); Query OK, 1 row affected (0.23 sec) mysql> insert into DemoTable values('678590'); Query OK, 1 row affected (0.46 sec) mysql> insert into DemoTable values('908765432'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values('222343388773'); Query OK, 1 row affected (0.35 sec) mysql> insert into DemoTable values('09028215'); Query OK, ...
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