Advanced PHP Interview Questions And Answers (Page 6)

Below are some important PHP interview questions which are asked in most MNC company interviews for beginners or professionals.

51.What is the maximum length of a table name, a database name, or a field name in MySQL?
Database name: 64 characters
Table name: 64 characters
Column name: 64 characters

52.How many values can the SET function of MySQL take?
MySQL SET function can take zero or more values, but at the maximum it can take 64 values.

53.What are the other commands to know the structure of a table using MySQL commands except EXPLAIN command?
DESCRIBE table_name;

54. How can we find the number of rows in a table using MySQL?
Use this for MySQL
SELECT COUNT(*) FROM table_name;

55.What’s the difference between md5(), crc32() and sha1() crypto on PHP?
The major difference is the length of the hash generated. CRC32 is, evidently, 32 bits, while sha1() returns a 128 bit value, and md5() returns a 160 bit value. This is important when avoiding collisions.

56.How can we find the number of rows in a result set using PHP?
Here is how can you find the number of rows in a result set in PHP:
$result = mysql_query($any_valid_sql, $database_link);
$num_rows = mysql_num_rows($result);
echo “$num_rows rows found”;

57.How many ways we can we find the current date using MySQL?
SELECT CURDATE();
SELECT CURRENT_DATE();
SELECT CURTIME();
SELECT CURRENT_TIME();

58.Give the syntax of GRANT commands?
The generic syntax for GRANT is as following
GRANT [rights] on [database] TO [username@hostname] IDENTIFIED BY [password]
Now rights can be:
a) ALL privilages
b) Combination of CREATE, DROP, SELECT, INSERT, UPDATE and DELETE etc.
We can grant rights on all databse by usingh *.* or some specific database by database.* or a specific table by database.table_name.Give the syntax of REVOKE commands?
The generic syntax for revoke is as following REVOKE [rights] on [database] FROM [username@hostname]
Now rights can be:
a) ALL privileges
b) Combination of CREATE, DROP, SELECT, INSERT, UPDATE and DELETE etc.We can
grant rights on all database by using *.* or some specific database by database.* or a specific table by database.table_name.

59.What is the difference between CHAR and VARCHAR data types?
CHAR is a fixed length data type. CHAR(n) will take n characters of storage even if you enter less than n characters to that column. For example, “Hello!” will be stored as “Hello! ” in CHAR(10) column.
VARCHAR is a variable length data type. VARCHAR(n) will take only the required storage for the actual number of characters entered to that column. For example, “Hello!” will be stored as “Hello!” in VARCHAR(10) column.

60.How can we encrypt and decrypt a data present in a mysql table using mysql?
AES_ENCRYPT() and AES_DECRYPT()
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