SELECT MEMBER.Name, MEMBER.Address, ORGANIZER.phoneNo, TRAVEL.Tour_Name, TRAVEL.Start_Date, TRAVEL.End_DateFROM TRAVEL RIGHT JOIN ((MEMBER LEFT JOIN ORGANIZER ON MEMBER.Member_ID=ORGANIZER.memberID) LEFT JOIN PARTICIPATION ON MEMBER.Member_ID=PARTICIPATION.MemberID) ON TRAVEL.TravelID=PARTICIPATION.TravelID;...

Cassandra is an open source distributed database, it combines dynamic key/value and column oriented feature of Bigtable.Features of Cassandra are:Flexible schema, no need to design schema first, it's very convenient to add or delete stringsSupport range search on keysHigh usability, extensible. The single node error will not affect the cluster.We can think Cassandra's data model as a 4 or 5 dimensional Hash.COLUMNColumns is the smallest data unit in Cassandra, it is a 3 dimensional data type including name,value and timestamp. { // This is a column name: "逖靖寒的�...

The difference is subtle, but it is a big difference. The ON condition stipulates which rows will be returned in the join, while the WHERE condition acts as a filter on the rows that actually were returned.Simple example: Consider a student table, consisting of one row per student, with student id and student name. In a second table, a list of grades that students have received, with student_id, subject, and grade. Give me a list of all students, and show their grade in Math. This requires a LEFT OUTER JOIN, because you want all students, and you know that some of them didn't take Math. Here a...

Blocking is a common occurrence in an SQL server context, but if you are new to the world of database management you might not know what this issue entails and perhaps even fear that it is a sign of serious underlying problems.To allay your fears and clear up the mystery, here is a brief overview of blocking and the steps you can take to tackle it.Image Source: PixabaySQL blocking explainedSQL blocking according to SentryOne is an offshoot of the way that concurrent databases operate. Because processes can be executed simultaneously, it is likely that at some point more than one process will n...