Group By

	Group By A GROUP BY statement in SQL specifies that a SQL SELECT statement partitions result rows into groups, based on their values in one or several columns. Typically, grouping is used to apply some sort of aggregate function for each group. The result of a query using a GROUP BY statement contains one row for each group. This implies constraints on the columns that can appear in the associated SELECT clause. As a general rule, the SELECT clause may only contain columns with a unique value per group. This includes columns that appear in the GROUP BY clause as well as aggregates resulting in one value per group. Examples Returns a list of Department IDs along with the sum of their sales for the date of January 1, 2000. SELECT DeptID, SUM(SaleAmount) FROM Sales WHERE SaleDate = '01-Jan-2000' GROUP BY DeptID Returns the data of the example pivot table which answers the question "How many Units did we sell in each Region for every Ship Date?": SELECT Region, Ship_Date, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Select (SQL) The SQL SELECT statement returns a result set of records, from one or more tables. A SELECT statement retrieves zero or more rows from one or more database tables or database views. In most applications, SELECT is the most commonly used data manipulation language (DML) command. As SQL is a declarative programming language, SELECT queries specify a result set, but do not specify how to calculate it. The database translates the query into a " query plan" which may vary between executions, database versions and database software. This functionality is called the " query optimizer" as it is responsible for finding the best possible execution plan for the query, within applicable constraints. The SELECT statement has many optional clauses: * SELECT clause is the list of columns or SQL expressions that must be returned by the query. This is approximately the relational algebra projection operation. * AS optionally provides an alias for each column or expression in the SELECT clause ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Aggregate Function In database management, an aggregate function or aggregation function is a function where the values of multiple rows are grouped together to form a single summary value. Common aggregate functions include: * Average (i.e., arithmetic mean) * Count * Maximum * Median * Minimum * Mode * Range * Sum Others include: * Nanmean (mean ignoring NaN values, also known as "nil" or "null") * Stddev Formally, an aggregate function takes as input a set, a multiset (bag), or a list from some input domain and outputs an element of an output domain . The input and output domains may be the same, such as for SUM, or may be different, such as for COUNT. Aggregate functions occur commonly in numerous programming languages, in spreadsheets, and in relational algebra. The listagg function, as defined in the SQL:2016 standard aggregates data from multiple rows into a single concatenated string. Decomposable aggregate functions Aggregate functions present a bottleneck, because they poten ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Pivot Table A pivot table is a table of grouped values that aggregates the individual items of a more extensive table (such as from a database, spreadsheet, or business intelligence program) within one or more discrete categories. This summary might include sums, averages, or other statistics, which the pivot table groups together using a chosen aggregation function applied to the grouped values. Although ''pivot table'' is a generic term, Microsoft held a trademark on the term in the United States from 1994 to 2020. History In their book ''Pivot Table Data Crunching'', Bill Jelen and Mike Alexander refer to Pito Salas as the "father of pivot tables". While working on a concept for a new program that would eventually become Lotus Improv, Salas noted that spreadsheets have patterns of data. A tool that could help the user recognize these patterns would help to build advanced data models quickly. With Improv, users could define and store sets of categories, then change views by dragging catego ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Aggregate Function In database management, an aggregate function or aggregation function is a function where the values of multiple rows are grouped together to form a single summary value. Common aggregate functions include: * Average (i.e., arithmetic mean) * Count * Maximum * Median * Minimum * Mode * Range * Sum Others include: * Nanmean (mean ignoring NaN values, also known as "nil" or "null") * Stddev Formally, an aggregate function takes as input a set, a multiset (bag), or a list from some input domain and outputs an element of an output domain . The input and output domains may be the same, such as for SUM, or may be different, such as for COUNT. Aggregate functions occur commonly in numerous programming languages, in spreadsheets, and in relational algebra. The listagg function, as defined in the SQL:2016 standard aggregates data from multiple rows into a single concatenated string. Decomposable aggregate functions Aggregate functions present a bottleneck, because they poten ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]