select sum(row_size) from ( select char_length(column1)+ char_length(column2)+ char_length(column3)+ char_length(column4) … <– repeat for all columns as row_size from your_table ) as tbl1; char_length for enum, set might not accurate, please take note
I was looking for an answer on the same subject, about “bulk/batch” update. People often describe the problem by comparing it with insert clause with multiple value sets (the “bulk” part). INSERT INTO mytable (mykey, mytext, myint) VALUES (1, ‘text1’, 11), (2, ‘text2’, 22), … Clear answer was still avoiding me, but I found the … Read more
Solr does not support updating individual fields yet, but there is a JIRA issue about this (almost 3 years old as of this writing). Until this is implemented, you have to update the whole document. UPDATE: as of Solr 4+ this is implemented, here’s the documentation.
If you ever plan on searching for specific attributes, it’s a bad idea to serialize them into a single column, since you’ll have to use per-row functions to get the information out – this rarely scales well. I would opt for your second choice. Have a list of attributes in an attribute table, the objects … Read more
I actually use this as one of my interview questions. The following is a good place to start: Addresses ——— AddressId (PK) Street1 … (etc) and AddressTypes ———— AddressTypeId AddressTypeName and UserAddresses (substitute “Company”, “Account”, whatever for Users) ————- UserId AddressTypeId AddressId This way, your addresses are totally unaware of how they are being used, … Read more
There is no “correct” name, but the academic name would be an “Associative Table” (see See the Wikipedia article Associative Entity). Other common names are (in alphabetical order): Association table Bridge table Cross-reference table Crosswalk Intermediary table Intersection table Join table Junction table Link table Linking table Many-to-many resolver Map table Mapping table Pivot Table … Read more
So I’ve been trying to figure out the real bottom-line when it comes to NoSQL vs RDBMS myself, and always end up with a response that doesn’t quite cut it. In my search there are really 2 primary differences between NoSQL and SQL, with only 1 being a true advantage. ACID vs BASE – NoSQL … Read more
A philosophical answer: Sub-optimal (relational) databases are rife with insert, update, and delete anomalies. These all lead to inconsistent data, resulting in poor data quality. If you can’t trust the accuracy of your data, what good is it? Ask yourself this: Do you want the right answers slower or do you want the wrong answers … Read more
There are four levels of constraint: column-level, row-level, table-level and schema-level. A table-level could, for example, involve a target table other than the source table on which it was declared but only gets checked when the source table changes. In theory a schema-level constraint would be checked for every change in every table in the … Read more