MySQLi Articles - Page 336 of 341

Suppose currently we are using a tutorial database so it would be the default MySQL database for subsequent queries. Now, with the help of USE db_name statement, we can change the default database to other given database subsequent queries.mysql> USE Sample Database changedThe database has been changed to Sample from the tutorial. To verify this we can run the following command −mysql> select database(); +------------+ | database() | +------------+ | sample     | +------------+ 1 row in set (0.00 sec)

Comparison operator between dates will work in a logical way. In the following example, while comparing two dates, MySQL is simply comparing two numbers or string −mysql> select 20171027 < 20150825; +---------------------------+ | 20171027 < 20150825       | +---------------------------+ |                      0    | +---------------------------+ 1 row in set (0.00 sec)The 0 output shows that the result of the above query is FALSE.mysql> select 20171027 > 20150825; +--------------------------+ | 20171027 > 20150825      | +--------------------------+ |                      1   | +--------------------------+ 1 row in set (0.00 sec)The output ‘1’ shows that the result of the above query is TRUE.

There is a database named test in the list of databases displayed by the statement SHOW DATABASES. We can use test database but the main disadvantage is that anything created in this database can be removed/changed by anyone else with access to it. To avoid this we should take permission from MySQL administrator to use a database of our own. For taking permission following command must be run − mysql> grant all on tutorial.* to root@localhost; Query OK, 0 rows affected (0.10 sec) In the above command, I am taking permission for the tutorial database. Root is the ... Read More

Conversion of TIME(N) and DATETIME(N) values to numeric form can be done by adding 0(+0) to them. Followings are the rules for such kind of conversion −Converted to INTEGERThe TIME(N) and DATETIME(N) values will be converted to an integer when N is 0.For example, the values of CURTIME() and NOW() can be converted to integer values as follows −mysql> SELECT CURTIME(), CURTIME()+0; +-----------+-------------------+ | CURTIME() | CURTIME()+0       | +-----------+-------------------+ | 19:42:54  | 194254            | +-----------+-------------------+ 1 row in set (0.04 sec) mysql> SELECT NOW(), NOW()+0; +-------------------------+----------------------------------+ | NOW()       ... Read More

As we know that this function converts a number of seconds into TIMESTAMP value. So by providing 0 seconds as the argument, it will give us the starting range of TIMESTAMP data type.mysql> Select FROM_UNIXTIME(0); +-------------------------+ | FROM_UNIXTIME(0)        | +-------------------------+ | 1970-01-01 05:30:00     | +-------------------------+ 1 row in set (0.00 sec)Now if we will change the argument from 0 to 60 seconds then the time will be changed by 01 minutes.mysql> Select FROM_UNIXTIME(60); +-------------------------+ | FROM_UNIXTIME(60)       | +-------------------------+ | 1970-01-01 05:31:00     | +-------------------------+ 1 row in set (0.00 sec)

As we know that with the help of MySQL UNIX_TIMESTAMP function, we can produce the number of seconds from given date/DateTime. But when we try to convert a date like ‘1965-05-15’ it would give 0(Zero) as output because the range of TIMESTAMP is between ‘1970-01-01 00:00:01’ to ‘2038-01-19 08:44:07’. Hence, the date values beyond TIMESTAMP range cannot be converted and will return 0 as output always.Examples are given below −mysql> Select UNIX_TIMESTAMP ('1965-05-15'); +----------------------------------------------+ | unix_timestamp('1965-05-15 05:04:30')        | +----------------------------------------------+ |                                   ... Read More

Actually, the case sensitivity of database and table name depends a lot on the case sensitivity of the underlying operating system. Hence, we can say that such names are not case sensitive in Windows but are case sensitive in most varieties of Unix.

CREATE DATABASE db_name can be used to create our own choice MySQL database. For example to create a database named Sample, we should have to run the command as follows −mysql> CREATE DATABASE Sample; Query OK, 1 row affected (0.04 sec)

For storing the date like ‘0000-00-00’ in a column of MySQL table, we must have to set the SQL mode to ‘allow_invalid_date’. Following example will demonstrate it −mysql> SET sql_mode = 'allow_invalid_dates'; Query OK, 0 rows affected, 1 warning (0.03 sec) mysql> Create table test_date(date_order date); Query OK, 0 rows affected (0.45 sec) mysql> Insert into test_date(date_order) values('0000-00-00'); Query OK, 1 row affected (0.04 sec) mysql> Select * from test_date; +------------+ | date_order | +------------+ | 0000-00-00 | +------------+ 1 row in set (0.00 sec)

YEAR(2) stores a year in 2-digit format. For example, we can write 69 to store 1969 a year. In YEAR (2), the year can be specified from 1970 to 2069 (70 to 69).YEAR(4) stores a year in 4-digit format. For example, we need to write 19669 to store 1969 as a year. In YEAR (4), the year can be specified from 1901 to 2155.MySQL interprets 2-digit year values with the assistance of following rules:Year values within the vary 00-69 are converted to 2000-2069.Year values in the range 70-99 are converted to 1970-1999.We must not store date values as a 2-digit ... Read More