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Found 6702 Articles for Database
![Chandu yadav](https://www.tutorialspoint.com/assets/profiles/22330/profile/60_142811-1519038104.jpg)
556 Views
To set auto increment initial value for MySQL table, use ALTER command. The first step would bealter table yourTableName modify yourColumnName int NOT NULL AUTO_INCREMENT PRIMARY KEY, add index(yourColumnName);The second step is as followsalter table yourTableName AUTO_INCREMENT=yourStartingValue;To understand the above syntax, let us create a table. The query to create a table is as followsmysql> create table setAutoIncrementDemo -> ( -> UserId int, -> UserName varchar(20) -> ); Query OK, 0 rows affected (0.75 sec)Now implement the above two steps to set auto increment initial value for MySQL table.Step 1 -The query is as followsmysql> alter ... Read More
![Arjun Thakur](https://www.tutorialspoint.com/assets/profiles/13574/profile/60_74441-1560315595.jpg)
580 Views
Let us see an example and create a table first.mysql> create table Add1ToExistingValue -> ( -> Value int -> ); Query OK, 0 rows affected (0.56 sec)Insert some records in the table using insert command.The query is as followsmysql> insert into Add1ToExistingValue values(10); Query OK, 1 row affected (0.12 sec) mysql> insert into Add1ToExistingValue values(13); Query OK, 1 row affected (0.15 sec) mysql> insert into Add1ToExistingValue values(15); Query OK, 1 row affected (0.13 sec) mysql> insert into Add1ToExistingValue values(16); Query OK, 1 row affected (0.14 sec) mysql> insert into Add1ToExistingValue values(20); Query OK, 1 row affected (0.16 sec) mysql> insert into Add1ToExistingValue values(40); Query OK, 1 row affected (0.15 sec) mysql> insert into Add1ToExistingValue values(50); Query OK, 1 row affected (0.11 sec) mysql> insert into Add1ToExistingValue values(55); Query OK, 1 row affected (0.17 sec) mysql> insert into Add1ToExistingValue values(56); Query OK, 1 row affected (0.17 sec)Display all records from the table using select statement.The query is as followsmysql> select *from Add1ToExistingValue;The following is the output+-------+ | Value | +-------+ | 10 ... Read More
![Smita Kapse](https://www.tutorialspoint.com/assets/profiles/13597/profile/60_103706-1512718957.jpg)
677 Views
Let us work around two cases −Case 1 − The syntax is as follows when the field is present and set to null.db.yourCollectionName.count({yourFieldName: null});Case 1 − The syntax is as follows when the field is not present and not set.db.yourCollectionName.count({yourFieldName: {$exists: false}});To understand both the above syntaxes, let us create a collection with the document. The query to create a collection with a document is as follows −> db.fieldIsNullOrNotSetDemo.insertOne({"EmployeeName":"Larry", "EmployeeAge":null, "EmployeeSalary":18500}); { "acknowledged" : true, "insertedId" : ObjectId("5c8a995c6cea1f28b7aa07fe") } > db.fieldIsNullOrNotSetDemo.insertOne({"EmployeeName":"Bob", "EmployeeAge":21, "EmployeeSalary":23500}); { "acknowledged" : true, "insertedId" : ObjectId("5c8a99836cea1f28b7aa07ff") } > db.fieldIsNullOrNotSetDemo.insertOne({"EmployeeName":"Carol", "EmployeeSalary":45500}); { ... Read More
![Ankith Reddy](https://www.tutorialspoint.com/assets/profiles/22328/profile/60_142162-1519038074.jpg)
638 Views
This type of error occurs when number of columns does not match whenever you are inserting records in the destination table. For a demo example, let us create a tablemysql> create table errorDemo -> ( -> User_Id int NOT NULL AUTO_INCREMENT, -> User_Name varchar(20), -> PRIMARY KEY(User_Id) -> ); Query OK, 0 rows affected (0.47 sec)The error is as followsmysql> insert into errorDemo values('John'); ERROR 1136 (21S01): Column count doesn't match value count at row 1To avoid this type of error, you need to use the following syntaxinsert into yourTableName(yourColumnName1, yourColumnName2, ...N)values(yourValue1, yourValue2, ....N);Insert some ... Read More
![Nishtha Thakur](https://www.tutorialspoint.com/assets/profiles/13598/profile/60_104893-1512719058.jpg)
119 Views
To find items that do not have a certain field, use the $exists operator. The syntax is as follows −> db.yourCollectionName.find({"yourItemName":{$exists:false}}).pretty();To understand the syntax, let us create a collection with the document. The query to create a collection with a document is as follows −> db.findDocumentDoNotHaveCertainFields.insertOne({"UserId":101, "UserName":"John", "UserAge":21}); { "acknowledged" : true, "insertedId" : ObjectId("5c8a95fb6cea1f28b7aa07fb") } > db.findDocumentDoNotHaveCertainFields.insertOne({"UserName":"David", "UserAge":22, "UserFavouriteSubject":["C", "Java"]}); { "acknowledged" : true, "insertedId" : ObjectId("5c8a96116cea1f28b7aa07fc") } > db.findDocumentDoNotHaveCertainFields.insertOne({"UserName":"Bob", "UserAge":24, "UserFavouriteSubject":["MongoDB", "MySQL"]}); { "acknowledged" : true, "insertedId" : ObjectId("5c8a96306cea1f28b7aa07fd") }Display all documents from a collection with the help of find() method. The ... Read More
![George John](https://www.tutorialspoint.com/assets/profiles/13511/profile/60_58410-1512537824.png)
149 Views
To revert rows to default column value, let us first create a demo tablemysql> create table defaultDemo -> ( -> Id int -> ); Query OK, 0 rows affected (0.48 sec)Insert some records in the table using insert command.The query is as followsmysql> insert into defaultDemo values(10); Query OK, 1 row affected (0.25 sec) mysql> insert into defaultDemo values(20); Query OK, 1 row affected (0.13 sec) mysql> insert into defaultDemo values(30); Query OK, 1 row affected (0.14 sec) mysql> insert into defaultDemo values(40); Query OK, 1 row affected (0.11 sec) mysql> insert into defaultDemo values(80); Query OK, ... Read More
![Anvi Jain](https://www.tutorialspoint.com/assets/profiles/13591/profile/60_98631-1512716973.jpg)
889 Views
PyMongo is a Python distribution containing tools for working with MongoDB. To perform regex queries with PyMongo, the syntax is as follows −db.yourCollectionName.find({'yourCollectionName':{'$regex':'^yourWords'}}).pretty();The above syntax will give all those documents that start from a specific word.To understand the syntax, let us create a collection with the document. The query to create a collection with a document is as follows −> db.performRegex.insertOne({"ClientName":"Larry", "ClientFolderInformation":[ "Folder 1", "Folder 2", "Folder 3", "Folder 4", "Folder 5"], "MainFolderLocation":"/MainFolder/Details/ClientFolder" }); { "acknowledged" : true, "insertedId" : ObjectId("5c8a8b186cea1f28b7aa07f2") } > db.performRegex.insertOne({"ClientName":"Larry", "ClientFolderInformation":[ "ClientFolder 1", "ClientFolder 2", "ClientFolder 3", "ClientFolder 4", "ClientFolder 5"], ... Read More
![Chandu yadav](https://www.tutorialspoint.com/assets/profiles/22330/profile/60_142811-1519038104.jpg)
1K+ Views
Let us first create a tablemysql> create table recordsDemo -> ( -> UserId int, -> Value int -> ); Query OK, 0 rows affected (0.52 sec)Now insert some records in the table using insert command.The query is as followsmysql> insert into recordsDemo values(1, 10); Query OK, 1 row affected (0.17 sec) mysql> insert into recordsDemo values(3, 598); Query OK, 1 row affected (0.18 sec) mysql> insert into recordsDemo values(5, 786); Query OK, 1 row affected (0.25 sec) mysql> insert into recordsDemo values(7, 189); Query OK, 1 row affected (0.16 sec) mysql> insert into recordsDemo values(9, 345); ... Read More
![Arjun Thakur](https://www.tutorialspoint.com/assets/profiles/13574/profile/60_74441-1560315595.jpg)
178 Views
Let us see how to loop through a stored procedure in MySQLmysql> DELIMITER // mysql> CREATE PROCEDURE do_WhileDemo(LastValue INT) -> BEGIN -> SET @loop = 0; -> REPEAT -> SET @loop= @loop+ 1; -> select @loop; -> UNTIL @loop >LastValue -> END REPEAT; -> END // Query OK, 0 rows affected (0.17 sec) mysql> DELIMITER ;Now call the stored procedure with the help of CALL command.The query is as followsmysql> call do_WhileDemo(10);The following is the output+-------+ | ... Read More
![Chandu yadav](https://www.tutorialspoint.com/assets/profiles/22330/profile/60_142811-1519038104.jpg)
100 Views
You need to use rand() function to select random result from MySQL.The syntax is as followsselect *from yourTableName order by rand() limit 1;To understand the above syntax, let us create a table. The query to create a table is as followsmysql> create table selectRandomRecord -> ( -> StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> StudentName varchar(20) -> ); Query OK, 0 rows affected (0.53 sec)Insert some records in the table using insert command.The query is as followsmysql> insert into selectRandomRecord(StudentName) values('John'); Query OK, 1 row affected (0.17 sec) mysql> insert into selectRandomRecord(StudentName) values('Carol'); Query OK, ... Read More