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Database Articles
Page 540 of 546
What data type to use for hashed password field in MySQL?
The hashed password data type depends upon which hashing algorithm we are using. The hashing algorithm does not depends upon the input size because it produces a result of the same length. It gives the result in a series of hexadecimal digits, and we can reduce the hexadecimal digits by half with the help of UNHEX() function. There are various algorithms and data types to store values. MD5 − It can use char(32) or BINARY(16). SHA-1 − It can use data type char(40) or BINARY(20). Example of MD5 The following is an example − mysql> select MD5('This ...
Read MoreHow long is the SHA256 hash in MySQL?
As the name “SHA256” suggest, it is 256 bits long. If we are using hexadecimal notation then digit codes represent 4 bits. In order to represent 256, we need 256/4 = 64 bits. We need a data type varchar(64) or char(64). Creating a table for our example. mysql> create table SHA256Demo -> ( -> Password varchar(64) -> ); Query OK, 0 rows affected (0.54 sec) Inserting records into table. mysql> insert into SHA256Demo values(' 4e2e1a39dba84a0b5a91043bb0e4dbef23970837'); Query OK, 1 row affected (0.18 sec) Displaying all records. mysql> select *From SHA256Demo; The following ...
Read MoreHow to shrink/ purge ibdata1 file in MySQL?
The ibdata1 file cannot shrink, it is a particularly troublesome feature of MySQL. The ibdata1 file can be shrinked if you delete all databases, remove the files and reload the mysqldump. We can configure MySQL so that each table, including its indexes, is stored as a separate file. It is enabled by default as of version 5.6.6 of MySQL. To setup our server to use separate files for each table, we need to change my.cnf in order to enable it. If your MySQL version is below 5.6.6, then you need to add it in my.cnf file. [mysqld] ...
Read MoreHow to create a temporary MySQL table in a SELECT statement without a separate CREATE TABLE?
To create a temporary table in a SELECT statement we use TEMPORARY keyword. This temporary table will be visible for the current session and whenever a session is closed, it is automatically destroyed. Two sessions can use the same temporary table. Creating a table. mysql> create table MyTableDemo -> ( -> id int, -> Name varchar(100) -> ); Query OK, 0 rows affected (0.69 sec) Inserting some records. mysql> insert into MyTableDemo values(1, 'John'); Query OK, 1 row affected (0.18 sec) mysql> insert into MyTableDemo values(2, 'Carol'); Query OK, 1 row affected (0.13 ...
Read MoreGet digits from a record in MySQL?
Use the function CONVERT() or Regular Expression. The CONVERT() method converts a value from one datatype to another. This will ecnetually fetch digits for us. Let us see an example. Firstly, we will create a table. mysql> create table textIntoNumberDemo -> ( -> Name varchar(100) -> ); Query OK, 0 rows affected (0.47 sec) Inserting some records. mysql> insert into textIntoNumberDemo values('John-11'); Query OK, 1 row affected (0.11 sec) mysql> insert into textIntoNumberDemo values('John-12'); Query OK, 1 row affected (0.17 sec) mysql> insert into textIntoNumberDemo values('John-2'); Query OK, 1 row affected (0.11 ...
Read MoreSwapping two column values in MySQL?
To swap two columns, we can apply the below swapping logic. Add both values and store them into the first column Subtract the first column’s value from the second and store it into the second column. Subtract the first column’s value from the updated second column and store it into the first. The above rule structure is as follows. Suppose, the first column is a and the second column is b. 1. a = a+b; 2. b = a-b; 3. a = a-b; Now we will apply the above rule in order to swap the two ...
Read MoreHow 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() ...
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