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MySQLi Articles
Page 94 of 341
How to insert NULL keyword as a value in a character type column of MySQL table having NOT NULL constraint?
It is quite possible to insert the NULL keyword as a value in a character type column having NOT NULL constraint because NULL is a value in itself. Following example will exhibit it −ExampleSuppose we have a table test2 having character type column ‘Name’ along with NOT NULL constraint on it. It can be checked from the DESCRIBE statement as follows −mysql> Describe test2\G *************************** 1. row *************************** Field: id Type: int(11) Null: NO Key: Default: NULL Extra: *************************** 2. row *************************** Field: NAME Type: varchar(20) Null: NO Key: ...
Read MoreHow can we remove NOT NULL constraint from a column of an existing MySQL table?
We can remove a NOT NULL constraint from a column of an existing table by using the ALTER TABLE statement.ExampleSuppose we have a table ‘test123’ having a NOT NULL constraint on column ‘ID’ as follows −mysql> DESCRIBE test123; +-------+---------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+---------+------+-----+---------+-------+ | ID | int(11) | NO | | NULL | | | Date | date | YES | | NULL | | +-------+---------+------+-----+---------+-------+ 2 rows in set (0.04 sec)Now if we ...
Read MoreHow can we apply a NOT NULL constraint to a column of an existing MySQL table?
We can apply the NOT NULL constraint to a column of an existing MySQL table with the help of ALTER TABLE statement. SyntaxALTER TABLE table_name MODIFY colum_name datatype NOT NULL; Examplemysql> Create table test123(ID INT, Date DATE); Query OK, 0 rows affected (0.19 sec) mysql> Describe test123; +-------+---------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+---------+------+-----+---------+-------+ | ID | int(11) | YES | | NULL | | | Date | date ...
Read MoreWhat happens when we apply NOT NULL constraint, with ALTER TABLE statement, to a column contains NULL values?
In this case, MySQL will return an error message regarding data truncated for the column. Following is an example of demonstrating it −ExampleSuppose we have a table ‘test2’ which contains a NULL value in column ‘ID’ at 2nd row. Now, if we will try to declare the column ID to NOT NULL then MySQL will return the error as follows −mysql> Select * from test2; +------+--------+ | ID | Name | +------+--------+ | 1 | Gaurav | | NULL | Rahul | +------+--------+ 2 rows in set (0.00 sec) mysql> ALTER TABLE TEST2 MODIFY ID INT NOT NULL; ERROR 1265 (01000): Data truncated for column 'ID' at row 2
Read MoreDifference between Simple and Complex View in SQL
Before discussing on Simple and complex, first we should know what is View. A View is the logical virtual table created from one or more tables which can be primarily used to fetch the columns from one or more different tables at a time. On the basis of tables involved in the view we can distinguish between Simple and Complex View in SQL.Following are the important differences between Simple and Complex View.Sr. No.KeySimple ViewComplex View1DefinitionSimple View in SQL is the view created by involving only single table. In other words we can say that there is only one base table ...
Read MoreWhat is the difference between BLOB and CLOB datatypes?
Blob and Clob together are known as LOB(Large Object Type). The following are the major differences between Blob and Clob data types.BlobClobThe full form of Blob is a Binary Large Object.The full form of Clob is Character Large Object.This is used to store large binary data.This is used to store large textual data.This stores values in the form of binary streams.This stores values in the form of character streams.Using this you can stores files like videos, images, gifs, and audio files.Using this you can store files like text files, PDF documents, word documents etc.MySQL supports this with the following datatypes:TINYBLOBBLOBMEDIUMBLOBLONGBLOBMySQL ...
Read MoreMySQL query to remove numbers after hyphen in a VARCHAR string with numbers
For this, use SUBSTRING_INDEX(). Let us first create a table −mysql> create table DemoTable2040 -> ( -> StudentCode varchar(20) -> ); Query OK, 0 rows affected (0.85 sec)Insert some records in the table using insert command −mysql> insert into DemoTable2040 values('John-232'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable2040 values('Carol-901'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable2040 values('David-987'); Query OK, 1 row affected (0.21 sec)Display all records from the table using select statement −mysql> select *from DemoTable2040;This will produce the following output −+-------------+ | StudentCode | +-------------+ | ...
Read MoreDisplaying only a list of records in ASC order with MySQL
To display a list of records in a specific order, you need to set conditions and use ORDER BY. For this, use ORDER BY CASE statement. Let us first create a table −mysql> create table DemoTable2039 -> ( -> Name varchar(20) -> ); Query OK, 0 rows affected (0.62 sec)Insert some records in the table using insert command −mysql> insert into DemoTable2039 values('John Doe'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable2039 values('John Smith'); Query OK, 1 row affected (0.08 sec) mysql> insert into DemoTable2039 values('Chris Brown'); Query OK, 1 row affected ...
Read MoreMySQL query to return TRUE for rows having positive value?
To return TRUE for positive values and FALSE for negative, use MySQL IF(). Let us first create a table −mysql> create table DemoTable2038 -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Value int -> ); Query OK, 0 rows affected (0.87 sec)Insert some records in the table using insert command −mysql> insert into DemoTable2038(Value) values(57); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable2038(Value) values(-100);; Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable2038(Value) values(-78); Query OK, 1 row affected (0.42 sec) mysql> insert into DemoTable2038(Value) ...
Read MoreFetch the first letter of a column value and insert it in another column with MySQL
For this, use the concept of LEFT() function. Let us first create a table −mysql> create table DemoTable2036 -> ( -> FirstLetter varchar(20), -> Title varchar(20) -> ); Query OK, 0 rows affected (1.01 sec)Insert some records in the table using insert command −mysql> insert into DemoTable2036(Title) values('Chris'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable2036(Title) values('John'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable2036(Title) values('Adam'); Query OK, 1 row affected (0.15 sec)Display all records from the table using select statement −mysql> select *from DemoTable2036;This will produce the ...
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