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Found 6702 Articles for Database
142 Views
To select one specific row and another random row, you can use ORDER BY and RAND(). Let us first create a sample table:mysql> create table oneSpecificRowAndOtherRandom -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Name varchar(20) -> ); Query OK, 0 rows affected (0.72 sec)Following is the query to insert some records in the table using insert command:mysql> insert into oneSpecificRowAndOtherRandom(Name) values('Larry'); Query OK, 1 row affected (0.56 sec) mysql> insert into oneSpecificRowAndOtherRandom(Name) values('Sam'); Query OK, 1 row affected (0.13 sec) mysql> insert into oneSpecificRowAndOtherRandom(Name) values('Mike'); Query OK, 1 row affected ... Read More
227 Views
In MySQL, AUTO_INCREMENT=3 tells that the inserted record will start from 3 not the default 1. Let us first create a sample table and set auto increment to 3:mysql> create table Auto_incrementDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Name varchar(20) -> )AUTO_INCREMENT=3; Query OK, 0 rows affected (0.52 sec)Following is the query to insert some records in the table using insert command:mysql> INSERT INTO Auto_incrementDemo(Name) values('John'); Query OK, 1 row affected (0.12 sec) mysql> INSERT INTO Auto_incrementDemo(Name) values('Larry'); Query OK, 1 row affected (0.15 sec) mysql> INSERT INTO Auto_incrementDemo(Name) ... Read More
508 Views
To count value for multiple columns, use the CASE statement. Let us first create a table::mysql> create table countValueMultipleColumnsDemo -> ( -> Value1 int, -> Value2 int, -> Value3 int -> ); Query OK, 0 rows affected (0.62 sec)Following is the query to insert some records in the table using insert command:mysql> insert into countValueMultipleColumnsDemo values(10, 15, 10); Query OK, 1 row affected (0.15 sec) mysql> insert into countValueMultipleColumnsDemo values(20, 30, 10); Query OK, 1 row affected (0.14 sec) mysql> insert into countValueMultipleColumnsDemo values(40, 10, 60); Query OK, 1 row affected (0.18 sec)Following ... Read More
4K+ Views
To change a primary key to auto_increment, you can use MODIFY command. Let us first create a table.mysql> create table changePrimaryKeyInAutoIncrement -> ( -> StudentId int not null primary key, -> StudentName varchar(100), -> StudentAge int, -> StudentAddress varchar(100) -> ); Query OK, 0 rows affected (0.63 sec)Let us now check the description of table using desc command:mysql> desc changePrimaryKeyInAutoIncrement;This will produce the following output+----------------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +----------------+--------------+------+-----+---------+-------+ | StudentId | int(11) ... Read More
545 Views
To get total number of fields in all tables in database, you can use information_schema.columns along with aggregate function count(*).We are using ‘sample’ database which consists of a lot of tables with fields. Following is the query to get total number of fields in all tables in database:mysql> SELECT COUNT(*) AS TOTAL_NUMBER_OF_FIELDS -> FROM INFORMATION_SCHEMA.COLUMNS -> WHERE TABLE_SCHEMA = 'sample';This will produce the following output+------------------------+ | TOTAL_NUMBER_OF_FIELDS | +------------------------+ | 796 | +------------------------+ 1 row in set (0.04 sec)Now, let us check another database ‘test’. Following is the query ... Read More
1K+ Views
To convert bool to int in MySQL, you can use CAST(). Let us first create a table:mysql> create table convertBoolToIntDemo -> ( -> isYoung bool -> ); Query OK, 0 rows affected (0.69 sec)Following is the query to insert some records in the table using insert command:mysql> insert into convertBoolToIntDemo values(true); Query OK, 1 row affected (0.18 sec) mysql> insert into convertBoolToIntDemo values(false); Query OK, 1 row affected (0.09 sec) mysql> insert into convertBoolToIntDemo values(true); Query OK, 1 row affected (0.15 sec) mysql> insert into convertBoolToIntDemo values(false); Query ... Read More
3K+ Views
To sort by character length in MySQL use the ORDER BY LENGTH(). Let us first create a table:mysql> create table orderingAADemo -> ( -> Value varchar(100) -> ); Query OK, 0 rows affected (1.30 sec)Following is the query to insert some records in the table using insert command:mysql> insert into orderingAADemo values('A'); Query OK, 1 row affected (0.12 sec) mysql> insert into orderingAADemo values('B'); Query OK, 1 row affected (0.13 sec) mysql> insert into orderingAADemo values('AA'); Query OK, 1 row affected (0.20 sec) mysql> insert into orderingAADemo values('C'); Query OK, 1 row affected (0.12 ... Read More
58 Views
To get the count of rows in which two or more specified values appear, let us first create a sample table:mysql> create table specifiedValuesDemo -> ( -> Value int, -> Value2 int, -> Value3 int -> ); Query OK, 0 rows affected (0.60 sec)Following is the query to insert some records in the table using insert command:mysql> insert into specifiedValuesDemo values(10, 15, 20); Query OK, 1 row affected (0.17 sec) mysql> insert into specifiedValuesDemo values(40, 10, 20); Query OK, 1 row affected (0.16 sec) ... Read More
81 Views
Use INFORMATION_SCHEMA.TABLES to display tables in sorted order. The below syntax will give sorted list of tables in ascending order:select TABLE_NAME from INFORMATION_SCHEMA.TABLES where TABLE_SCHEMA= 'yourDatabaseName' order by TABLE_NAME;Following is the query to implement the equivalent to SHOW TABLES:mysql> select TABLE_NAME from INFORMATION_SCHEMA.TABLES -> where TABLE_SCHEMA= 'sample' order by TABLE_NAME;This will produce the following output+------------------------------------+ | TABLE_NAME | +------------------------------------+ | a | | accumulateddemo ... Read More
846 Views
To suppress MySQL stored procedure output, you can use variable. Let us first create a table.mysql> create table person_information -> ( -> Id int, -> Name varchar(20) -> ); Query OK, 0 rows affected (0.50 sec)Following is the query to insert some records in the table using insert command:mysql> insert into person_information values(100, 'John'); Query OK, 1 row affected (0.17 sec) mysql> insert into person_information values(101, 'Chris'); Query OK, 1 row affected (0.22 sec) mysql> insert into person_information values(102, 'Robert'); Query OK, 1 row affected (0.16 sec)Following is the query to display records from ... Read More