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Database Articles
Page 415 of 546
Check if table exists in MySQL and display the warning if it exists?
To check if table exists, use the following syntax −CREATE TABLE IF NOT EXISTS yourTableName ( yourColumnName1 dataType, . . . . N );Here, we will try to create a table that already exists and then it will produce a warning message “Table already exists”. Let us first create a table. This table already exists −mysql> CREATE TABLE IF NOT EXISTS DemoTable ( Id int ); Query OK, 0 rows affected, 1 warning (0.06 sec)The warning message is as follows −mysql> show warnings;Output+-------+------+-------------------------------------+ | Level | Code | Message ...
Read MoreGet maximum and minimum value in MongoDB?
Use $max and $min operator along with aggregate framework to get the maximum and minimum value. Let us first create a collection with documents −> db.maxAndMinDemo.insertOne({"Value":98}); { "acknowledged" : true, "insertedId" : ObjectId("5cd698a357806ebf1256f129") } > db.maxAndMinDemo.insertOne({"Value":97}); { "acknowledged" : true, "insertedId" : ObjectId("5cd698af57806ebf1256f12a") } > db.maxAndMinDemo.insertOne({"Value":69}); { "acknowledged" : true, "insertedId" : ObjectId("5cd698b357806ebf1256f12b") } > db.maxAndMinDemo.insertOne({"Value":96}); { "acknowledged" : true, "insertedId" : ObjectId("5cd698b657806ebf1256f12c") } > db.maxAndMinDemo.insertOne({"Value":99}); { "acknowledged" : true, "insertedId" : ObjectId("5cd698b957806ebf1256f12d") }Following is the query to display all documents from a collection with the help of find() method ...
Read MoreConcatenate two tables in MySQL with a condition?
To concatenate two tables, UNION ALL in MySQL. Let us create a table −mysql> create table DemoTable1 ( Id int, FirstName varchar(20) ); Query OK, 0 rows affected (1.52 sec)Insert some records in the table using insert command −mysql> insert into DemoTable1 values(10, 'John'); Query OK, 1 row affected (0.28 sec) mysql> insert into DemoTable1 values(20, 'Carol'); Query OK, 1 row affected (0.28 sec)Display all records from the table using select statement −mysql> select *from DemoTable1;Output+------+-----------+ | Id | FirstName | +------+-----------+ | 10 | John | ...
Read MoreHow to find documents with exactly the same array entries as in a MongoDB query?
For this, use the $all operator. Let us first create a collection with documents −>db.findDocumentExactlySameInArrayDemo.insertOne({"TechnicalSubjects":["C++", "Java", "MongoDB"]}); { "acknowledged" : true, "insertedId" : ObjectId("5cd69a5f57806ebf1256f12e") } >db.findDocumentExactlySameInArrayDemo.insertOne({"TechnicalSubjects":["MySQL", "Java", "MongoDB"]}); { "acknowledged" : true, "insertedId" : ObjectId("5cd69ac057806ebf1256f12f") } >db.findDocumentExactlySameInArrayDemo.insertOne({"TechnicalSubjects":["C#", "Python", "MongoDB"]}); { "acknowledged" : true, "insertedId" : ObjectId("5cd69ad457806ebf1256f130") } >db.findDocumentExactlySameInArrayDemo.insertOne({"TechnicalSubjects":["MySQL", "C", "MongoDB"]}); { "acknowledged" : true, "insertedId" : ObjectId("5cd69adf57806ebf1256f131") }Following is the query to display all documents from a collection with the help of find() method −> db.findDocumentExactlySameInArrayDemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5cd69a5f57806ebf1256f12e"), "TechnicalSubjects" : [ ...
Read MoreHow to search between columns in MySQL?
Use BETWEEN clause to search between columns. Let us first create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, Score1 int, Score2 int ); Query OK, 0 rows affected (0.78 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(Score1, Score2) values(45, 65); Query OK, 1 row affected (0.26 sec) mysql> insert into DemoTable(Score1, Score2) values(450, 680); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable(Score1, Score2) values(800, 900); Query OK, 1 row affected (0.17 sec)Display all records from the table using select statement ...
Read MoreGetting a list of values by using MongoDB $group?
To get a list of values, use $group aggregation along with $push operator. Let us first create a collection with documents −> db.groupByDemo.insertOne({"UserName":"John", "Subject":"MongoDB"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd69f0457806ebf1256f136") } > db.groupByDemo.insertOne({"UserName":"Larry", "Subject":"MySQL"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd69f0657806ebf1256f137") } > db.groupByDemo.insertOne({"UserName":"John", "Subject":"Java"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd69f0d57806ebf1256f138") } > db.groupByDemo.insertOne({"UserName":"John", "Subject":"C"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd69f1357806ebf1256f139") } > db.groupByDemo.insertOne({"UserName":"Larry", "Subject":"SQL Server"}); { "acknowledged" : true, "insertedId" : ObjectId("5cd69f1c57806ebf1256f13a") }Following is the query to display all documents from a collection with the help ...
Read MoreHow to exclude _id without including other fields using the aggregation framework in MongoDB?
Let us first create a collection with documents −> db.excludeIdDemo.insertOne({"StudentFirstName":"John", "StudentAge":21}); { "acknowledged" : true, "insertedId" : ObjectId("5cd701a56d78f205348bc632") } > db.excludeIdDemo.insertOne({"StudentFirstName":"Robert", "StudentAge":20}); { "acknowledged" : true, "insertedId" : ObjectId("5cd701af6d78f205348bc633") } > db.excludeIdDemo.insertOne({"StudentFirstName":"Chris", "StudentAge":24}); { "acknowledged" : true, "insertedId" : ObjectId("5cd701b86d78f205348bc634") }Following is the query to display all documents from a collection with the help of find() method −> db.excludeIdDemo.find();This will produce the following output −{ "_id" : ObjectId("5cd701a56d78f205348bc632"), "StudentFirstName" : "John", "StudentAge" : 21 } { "_id" : ObjectId("5cd701af6d78f205348bc633"), "StudentFirstName" : "Robert", "StudentAge" : 20 } { "_id" : ObjectId("5cd701b86d78f205348bc634"), "StudentFirstName" : "Chris", "StudentAge" ...
Read MoreHow to implement MongoDB $or operator
Evaluate one or more expressions using the $or operator in MongoDB. Following is the syntax −db.yourCollectionName.find({ $or: [{ "yourFieldName": yourValue1 }, { "yourFieldName": yourValue2} ] } ).pretty();Let us first create a collection with documents −> db.orOperatorDemo.insertOne({"StudentNames":["John", "Carol", "Sam"]}); { "acknowledged" : true, "insertedId" : ObjectId("5cd6b80a6d78f205348bc61b") } > db.orOperatorDemo.insertOne({"StudentNames":["Robert", "Chris", "David"]}); { "acknowledged" : true, "insertedId" : ObjectId("5cd6b8266d78f205348bc61c") } > db.orOperatorDemo.insertOne({"StudentNames":["John"]}); { "acknowledged" : true, "insertedId" : ObjectId("5cd6b8346d78f205348bc61d") }Following is the query to display all documents from a collection with the help of find() method −> db.orOperatorDemo.find().pretty();This will produce the following output −{ "_id" ...
Read MoreDisplay dates after NOW() + 10 days from a MySQL table?
You can use DATE_ADD() function with where clause for this. Let us first create a table −mysql> create table DemoTable ( ShippingDate date ); Query OK, 0 rows affected (0.54 sec)Note : The current date and time is as follows, we found using NOW() −mysql> select now(); +-----------------------+ | now() | +-----------------------+ | 2019-06-04 20 :43 :57 | +-----------------------+ 1 row in set (0.00 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('2019-06-16'); Query OK, 1 ...
Read MoreUpdate multiple rows in a single MongoDB query?
Use the concept of initializeUnorderedBulkOp(). Let us first create a collection with documents −>db.upDateMultipleRowsDemo.insertOne({"CustomerName":"John", "CustomerPurchaseAmount":500}); { "acknowledged" : true, "insertedId" : ObjectId("5cd6ceb06d78f205348bc626") } >db.upDateMultipleRowsDemo.insertOne({"CustomerName":"Chris", "CustomerPurchaseAmount":700}); { "acknowledged" : true, "insertedId" : ObjectId("5cd6ceb26d78f205348bc627") } >db.upDateMultipleRowsDemo.insertOne({"CustomerName":"David", "CustomerPurchaseAmount":50}); { "acknowledged" : true, "insertedId" : ObjectId("5cd6ceb36d78f205348bc628") } >db.upDateMultipleRowsDemo.insertOne({"CustomerName":"Larry", "CustomerPurchaseAmount":1900}); { "acknowledged" : true, "insertedId" : ObjectId("5cd6ceb46d78f205348bc629") }Following is the query to display all documents from a collection with the help of find() method −> db.upDateMultipleRowsDemo.find().pretty();This will produce the following output −{ "_id" : ObjectId("5cd6ceb06d78f205348bc626"), "CustomerName" : "John", "CustomerPurchaseAmount" : 500 } { ...
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