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Articles by AmitDiwan
Page 796 of 840
MySQL query to compare and display only the rows with NULL values
For this, you can use IFNULL(). Let us first create a table −mysql> create table DemoTable ( Value1 int, Value2 int ); Query OK, 0 rows affected (0.75 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(10, NULL); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable values(20, 40); Query OK, 1 row affected (0.27 sec) mysql> insert into DemoTable values(3, NULL); Query OK, 1 row affected (0.20 sec)Display all records from the table using select statement −mysql> select *from DemoTable;This will produce the following output −+--------+--------+ | Value1 | Value2 ...
Read MoreMySQL UNIQUE declaration to avoid inserting duplicate values?
Following is the declaration for a UNIQUE clause in MySQL −create table yourTableName ( yourColumnName1 dataType, yourColumnName2 dataType, UNIQUE(yourColumnName1), UNIQUE(yourColumnName1) );Let us first create a table −mysql> create table DemoTable ( Value int, Value2 int, UNIQUE(Value), UNIQUE(Value2) ); Query OK, 0 rows affected (13.98 sec)Insert some records in the table using insert command. Here, duplicate records won’t insert because we have used UNIQUE above −mysql> insert into DemoTable values(10, 20) ; Query OK, 1 row affected (0.32 sec) mysql> insert into DemoTable values(10, 30); ERROR 1062 (23000): Duplicate entry '10' for key ...
Read MoreDisplay distinct dates in MySQL from a column with date records
Let us first create a table −mysql> create table DemoTable ( AdmissionDate datetime ); Query OK, 0 rows affected (8.99 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('2010-01-10 12:30:45'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values('2010-01-10 12:30:45'); Query OK, 1 row affected (0.46 sec) mysql> insert into DemoTable values('2010-01-10 12:30:45'); Query OK, 1 row affected (0.71 sec) mysql> insert into DemoTable values('2010-01-12 12:30:45'); Query OK, 1 row affected (1.22 sec) mysql> insert into DemoTable values('2010-01-20 12:30:45'); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable values('2010-01-20 ...
Read MoreGet all the tables from a MySQL database having a specific column, let's say xyz?
Let’s say we have a database “web” and we need to get all the tables having a specific column ’StudentFirstName’.For this, below is the query −mysql> select myColumnName.table_name from information_schema.columns myColumnName where myColumnName.column_name = 'StudentFirstName' and table_schema='web';This will produce the following output −+---------------+ | TABLE_NAME | +---------------+ | demotable109 | | demotable297 | | demotable335 | | demotable395 | | demotable418 | | demotable425 | | demotable436 | +---------------+ 7 rows in set (0.14 sec)Therefore, the above tables have one of the column names as “StudentFirstName”.Let us check the description ...
Read MoreHow can I replace & with an ampersand in my MySQL database?
To replace & with an ampersand, use MySQL REPLACE(). Let us first create a table −mysql> create table DemoTable( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, Value varchar(100) ); Query OK, 0 rows affected (1.06 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(Value) values('@amp'); Query OK, 1 row affected (0.33 sec) mysql> insert into DemoTable(Value) values('&'); Query OK, 1 row affected (1.09 sec) mysql> insert into DemoTable(Value) values('#amp'); Query OK, 1 row affected (0.28 sec)Display all records from the table using select statement −mysql> select *from DemoTable;This will produce the following output −+----+-------+ ...
Read MoreFind average on the basis of corresponding duplicate VARCHAR values in MySQL
Let us first create a table −mysql> create table DemoTable( Value int, Value2 varchar(100) ); Query OK, 0 rows affected (0.84 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(10, '999.999.999.999'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values(20, '888.888.888.888'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values(30, '999.999.999.999'); Query OK, 1 row affected (0.09 sec)Display all records from the table using select statement −mysql> select *from DemoTable;This will produce the following output −+-------+-----------------+ | Value | Value2 ...
Read MoreCan we perform MySQL UPDATE and change nothing in a table?
Yes, we can do that. Let us first create a table −mysql> create table DemoTable( Id int ); Query OK, 0 rows affected (1.02 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(201); Query OK, 1 row affected (0.22 sec) mysql> insert into DemoTable values(202); Query OK, 1 row affected (0.09 sec) mysql> insert into DemoTable values(290); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable values(301); 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 MoreWhat does select @@identity do in MySQL?
The @@identity returns the last inserted value in the auto_increment column in the current session. Let us first create a table −mysql> create table DemoTable( UserId int NOT NULL AUTO_INCREMENT PRIMARY KEY, UserName varchar(100) ); Query OK, 0 rows affected (0.67 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(UserName) values('David'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable(UserName) values('Mike'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable(UserName) values('Carol'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable(UserName) values('Robert'); Query OK, 1 row affected (0.24 sec) ...
Read MoreMySQL query to fetch the maximum corresponding value from duplicate column values
Let us first create a table −mysql> create table DemoTable( ProductName varchar(100), ProductPrice int ); Query OK, 0 rows affected (0.68 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('Product-1', 56); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values('Product-2', 78); Query OK, 1 row affected (0.23 sec) mysql> insert into DemoTable values('Product-1', 88); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values('Product-2', 86); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable values('Product-1', 45); Query OK, 1 row affected (0.18 sec) mysql> insert into ...
Read MoreWill extending the size of a varchar field in MySQL affect the data inside it?
If you will extend the size of a varchar field in MySQL then it won’t affect the data inside it.Let us first create a table −mysql> create table DemoTable( Name varchar(8) ); Query OK, 0 rows affected (1.11 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('John'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable values('Robert'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values('Mike'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values('Sam'); Query OK, 1 row affected (0.13 sec)Display all records from the ...
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