Add STD alias to stddevPop function for MySQL compatibility

docs/en/sql-reference/aggregate-functions/reference/stddevpop.md

@@ -7,6 +7,10 @@ sidebar_position: 30
 
 The result is equal to the square root of [varPop](../../../sql-reference/aggregate-functions/reference/varpop.md).
 
-:::note    
+Alias:
+- `STD`
+- `STDDEV_POP`
+
+:::note
 This function uses a numerically unstable algorithm. If you need [numerical stability](https://en.wikipedia.org/wiki/Numerical_stability) in calculations, use the `stddevPopStable` function. It works slower but provides a lower computational error.
 :::

docs/en/sql-reference/aggregate-functions/reference/stddevsamp.md

@@ -7,6 +7,8 @@ sidebar_position: 31
 
 The result is equal to the square root of [varSamp](../../../sql-reference/aggregate-functions/reference/varsamp.md).
 
-:::note    
+Alias: `STDDEV_SAMP`.
+
+:::note
 This function uses a numerically unstable algorithm. If you need [numerical stability](https://en.wikipedia.org/wiki/Numerical_stability) in calculations, use the `stddevSampStable` function. It works slower but provides a lower computational error.
 :::

docs/en/sql-reference/aggregate-functions/reference/varpop.md

@@ -9,6 +9,8 @@ Calculates the amount `Σ((x - x̅)^2) / n`, where `n` is the sample size and `x
 
 In other words, dispersion for a set of values. Returns `Float64`.
 
-:::note    
+Alias: `VAR_POP`.
+
+:::note
 This function uses a numerically unstable algorithm. If you need [numerical stability](https://en.wikipedia.org/wiki/Numerical_stability) in calculations, use the `varPopStable` function. It works slower but provides a lower computational error.
 :::

docs/en/sql-reference/aggregate-functions/reference/varsamp.md

@@ -11,6 +11,8 @@ It represents an unbiased estimate of the variance of a random variable if passe
 
 Returns `Float64`. When `n <= 1`, returns `+∞`.
 
-:::note    
+Alias: `VAR_SAMP`.
+
+:::note
 This function uses a numerically unstable algorithm. If you need [numerical stability](https://en.wikipedia.org/wiki/Numerical_stability) in calculations, use the `varSampStable` function. It works slower but provides a lower computational error.
 :::

src/AggregateFunctions/AggregateFunctionSecondMoment.cpp

@@ -19,6 +19,7 @@ void registerAggregateFunctionsStatisticsSecondMoment(AggregateFunctionFactory &
     factory.registerAlias("VAR_POP", "varPop", AggregateFunctionFactory::CaseInsensitive);
     factory.registerAlias("STDDEV_SAMP", "stddevSamp", AggregateFunctionFactory::CaseInsensitive);
     factory.registerAlias("STDDEV_POP", "stddevPop", AggregateFunctionFactory::CaseInsensitive);
+    factory.registerAlias("STD", "stddevPop", AggregateFunctionFactory::CaseInsensitive);
 }
 
 }

tests/queries/0_stateless/02833_std_alias.reference

@@ -0,0 +1,2 @@
+6.408619196051518	5.848925577403085
+6.408619196051518	5.848925577403085

tests/queries/0_stateless/02833_std_alias.sql

@@ -0,0 +1,8 @@
+DROP TABLE IF EXISTS series;
+CREATE TABLE series(i UInt32, x Float64, y Float64) ENGINE = Memory;
+INSERT INTO series(i, x, y) VALUES (1, 5.6,-4.4),(2, -9.6,3),(3, -1.3,-4),(4, 5.3,9.7),(5, 4.4,0.037),(6, -8.6,-7.8),(7, 5.1,9.3),(8, 7.9,-3.6),(9, -8.2,0.62),(10, -3,7.3);
+
+SELECT std(x), std(y) FROM series;
+SELECT stddevPop(x), stddevPop(y) FROM series;
+
+DROP TABLE series;