For instance, you can nest COALESCE to handle successive levels of default values. If the first expression within the COALESCE function returns NULL, it moves to the next expression, evaluating until a non-null value is obtained or reaches the end of the chain. This nesting helps in creating ...
机器学习技法 之 聚合模型总结(Summary of Aggregation Models) Blending Models(融合模型) Blending:指的是当已有丰富多样的 gtg_tgt 时,进行聚合(Aggregate)。(aggregate after getting diverse gtg_tgt)。 常用的三种 Blending 模型如下: uniform : 是认为不同的 gtg_tgt 之间可能可以相互修正,从而提高...
A columnar database is a type of database management system (DBMS) that stores tables of data in columns rather than rows. Unlike traditional row-based databases, which store data sequentially in rows, columnar databases store data in columns. These databases allow for more efficient data retriev...
onebrc: aggregation of 1 billion rows (of historical data) from the 1 billion row challenge is fast, out-of-the-box. This is because Proton is based on ClickHouse, an open-source column-oriented DBMS for OLAP workloads. real-time-ai: build real-time RAG with open source tools: load re...
sidbidday Example: Find sid’s of sailors who’ve reserved a red or a green boat UNION : Can be used to compute the union of any two union- compatible sets of tuples (which are themselves the result of SQL queries). If we replace OR by AND in the first version, what do we get...