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Database Articles
Page 541 of 546
How do I check to see if a value is an integer in MySQL?
To check if the given value is a string or not ,we use the cast() function. If the value is not numeric then it returns 0, otherwise it will return the numeric value. In this way, we can check whether the value is an integer or not. Case 1 − Checking for a string with integers mysql> select cast('John123456' AS UNSIGNED); The following is the output. It shows that the value is not numeric, therefore 0 is returned. +--------------------------------+ | cast('John123456' AS UNSIGNED) | +--------------------------------+ | 0 | +--------------------------------+ 1 row in set, 1 warning (0.00 sec) ...
Read MoreHow can I tell when a MySQL table was last updated?
We can know that with the help of the column name ‘UPDATED_TIME’ using information_schema.tables with WHERE clause. Let us first create a table for our example. mysql> create table MyISAMTableDemo -> ( -> id int -> ); Query OK, 0 rows affected (0.56 sec) Inserting some records into table. mysql> insert into MyISAMTableDemo values(1); Query OK, 1 row affected (0.72 sec) mysql> insert into MyISAMTableDemo values(2); Query OK, 1 row affected (0.16 sec) Syntax to know the last updated time. SELECT UPDATE_TIME FROM information_schema.tables WHERE TABLE_SCHEMA = 'yourDatabaseName' AND TABLE_NAME = ...
Read MoreHow to subtract 10 days from the current datetime in MySQL?
Firstly, let us get the current datetime with the help of the now() function. mysql> select now(); The following is the output. +---------------------+ | now() | +---------------------+ | 2018-11-01 19:55:56 | +---------------------+ 1 row in set (0.00 sec) Syntax to subtract 10 days with the help of DATE_SUB() select DATE_SUB(now(),interval integer_value day ); Applying the above syntax to subtract 10 days from the current datetime. mysql> select DATE_SUB(now(),interval 10 day); Here is the output. +---------------------------------+ | DATE_SUB(now(),interval 10 day) | +---------------------------------+ | 2018-10-22 19:56:07 | +---------------------------------+ 1 row in set (0.00 sec)
Read MoreGet the new record key ID from MySQL insert query?
We can get new record key with the help of LAST_INSERT_ID() function from MySQL. First, we will create a table and for inserting record, we will use LAST_INSERT_ID(). Let us create a table with the help of create command. The query is as follows − mysql> create table LastInsertRecordIdDemo -> ( -> id int auto_increment, -> value varchar(100), -> primary key(id) -> ); Query OK, 0 rows affected (0.52 sec) After creating a table, we will insert records and set it using LAST_INSERT_ID() ...
Read MoreFind rows that have the same value on a column in MySQL?
First, we will create a table and insert some values into the table. Let us create a table. mysql> create table RowValueDemo -> ( -> Name varchar(100) -> ); Query OK, 0 rows affected (0.69 sec) Insert records using the insert command. We have added duplicate values as well for our example. mysql> insert into RowValueDemo values('John'); Query OK, 1 row affected (0.14 sec) mysql> insert into RowValueDemo values('Bob'); Query OK, 1 row affected (0.14 sec) mysql> insert into RowValueDemo values('Carol'); Query OK, 1 row affected ...
Read MoreMySQL status in terms of active or total connections?
The active or total connection can be known with the help of threads_connected variable. The variable tells about the number of currently open connections. The query is as follows − mysql> show status where `variable_name` = 'Threads_connected'; Here is the output. +-------------------+-------+ | Variable_name | Value | +-------------------+-------+ | Threads_connected | 1 | +-------------------+-------+ 1 row in set (0.06 sec) We can check the same with the help of show command. The query is as follows − mysql> show processlist; Here is the output. +----+-----------------+-----------------+----------+---------+--------+------------------------+------------------+ ...
Read MoreCount the number of occurrences of a string in a VARCHAR field in MySQL?
To count the number of occurrences of a string in a VARCHAR, we can use the logic of subtraction with length. First, we will create a table with the help of create command. mysql> create table StringOccurrenceDemo -> ( -> Cases varchar(100), -> StringValue varchar(500) -> ); Query OK, 0 rows affected (0.56 sec) After executing the above table, we will insert records into the table. The query is as follows − mysql> insert into StringOccurrenceDemo values('First', 'This is MySQL Demo and MySQL is ...
Read MoreRank function in MySQL?
The rank() function can be used to give a rank for every row within the partition of a result set. First, let us create a table − mysql> create table RankDemo mysql> ( mysql> id int mysql> ); Query OK, 0 rows affected (0.53 sec) Inserting records into table. mysql> insert into RankDemo values(1); Query OK, 1 row affected (0.19 sec) mysql> insert into RankDemo values(3); Query OK, 1 row affected (0.12 sec) mysql> insert into RankDemo values(3); Query OK, 1 row affected (0.11 ...
Read MoreWhat is the operator <=> in MySQL?
Here are the usages of the operator in MySQL. Case 1 This operator is similar to = operator i.e. when the value is equal then the result will become true(1), otherwise false(0). In the first case both = and operators work same. Case 2 Whenever we compare any value with NULL then the operator gives the value 0 and when we compare with NULL NULL, then it returns 1. While in case of = operator, this does not happen. Whenever we compare any value with NULL, it returns NULL. If we compare NULL with NULL, then ...
Read MoreHow to set NOW() as default value for datetime datatype in MySQL?
We can set the now() function as a default value with the help of dynamic default. First, we will create a table with data type” datetime”. After that, we will set now() as the default value for column “MyTime” as shown below. Creating a table. mysql> create table DefaultDateTimeDemo -> ( -> MyTime datetime default CURRENT_TIMESTAMP -> ); Query OK, 0 rows affected (0.59 sec) After creating the above table, we won’t insert any value while using the insert command. This is done so that we can get the ...
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