Query 2: SELECT * FROM tablename WHERE b = 145. You could add an index on B for this second query. So you'd have 2 indexes, (a,b) and (b). But indexes take place, they take time to update, etc. So in this case, perhaps you'd be better off with a single index that coul...
ENUM values, when stored are converted into numbers against each column value which results in a considerable memory saving for tables having a large no of records i.e. suppose we have an ENUM having values – value1, value2, and value3 then actual memory storage would be numeric indexes 1...
MySQL 8.0 delivers support for indexes in descending order. Values in such an index are arranged in descending order, and we scan it forward. Before 8.0, when a user create a descending index, we created an ascending index and scanned it backwards. One benefit is that forward index scans ar...
Indexes are ordered based on their keys. Loose index scan effectively jumps from one unique value (or set of values) to the next based on the index’s prefix keys. In the above query column “c1” is the prefix of the index “c1_c2_idx”. Loose index scan jumps to the unique values...
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MySQL Searching using Regular Expression MySQL Concatenating fields MySQL Text functions MySQL Date Time functions MySQL numeric manipulation functions MySQL Group By MySQL Table MySQL Data Type MySQL Sequences MySQL Indexes MySQL Subquery MySQL Joins MySQL Union MySQL full text searching MySQL Insert State...
Locks Used in MySQLDefining and Calling Stored ProceduresVariables, Loops and Cursors Used in Stored ProceduresSystem, User-Defined and Stored Procedure VariablesMySQL Server AdministrationStorage Engines in MySQL ServerInnoDB Storage Engine - Primary and Secondary IndexesPerformance Tuning and Optimization...
Are indexes only found in books? No, indexes can also be found in long reports, manuals, and academic papers, wherever detailed navigation is helpful. 4 Why might a document lack an index? Creating an index is time-consuming and may not be necessary for shorter or less complex documents. ...
What are ENUMs used for in MySQL? Using Enum can restrict the number of values that can be allowed to go inside a table. If there is an ENUM for Colors ENUM(‘blue’,’yellow’,’green’) I can use an insert statement like Insert colors values (‘red’). ...
cardinality at first. I think place the field with bigger cardinality at first, the index can be used for both "where a = x and b = y" and "where b = x and a = y". However, as for the only one query "where a = x and b = y", the two indexes are the same on ...