Register COALESCE function. Update docs. Add integration test to engine.

README.md

@@ -61,6 +61,7 @@ We support and actively test against certain third-party clients to ensure compa
 - `ARRAY_LENGTH(json)`: If the json representation is an array, this function returns its size.
 - `SPLIT(str,sep)`: Receives a string and a separator and returns the parts of the string split by the separator as a JSON array of strings.
 - `CONCAT(...)`: Concatenate any group of fields into a single string.
+- `COALESCE(...)`: The function returns the first non-null value in a list.
 
 ## Example
 
@@ -122,7 +123,7 @@ func createTestDatabase() *mem.Database {
     for _, row := range rows {
         table.Insert(ctx, row)
     }
-    
+
     return db
 }
 

SUPPORTED.md

@@ -78,6 +78,7 @@
 - IS_BINARY
 - SPLIT
 - SUBSTRING
+- COALESCE
 
 ## Time functions
 - DAY

engine_test.go

@@ -295,6 +295,18 @@ var queries = []struct {
 			{string("abc")},
 		},
 	},
+	{
+		`SELECT COALESCE(NULL, NULL, NULL, 'example', NULL, 1234567890)`,
+		[]sql.Row{
+			{string("example")},
+		},
+	},
+	{
+		`SELECT COALESCE(NULL, NULL, NULL, COALESCE(NULL, 1234567890))`,
+		[]sql.Row{
+			{int64(1234567890)},
+		},
+	},
 	{
 		"SELECT concat(s, i) FROM mytable",
 		[]sql.Row{

sql/expression/function/registry.go

@@ -34,10 +34,11 @@ var Defaults = sql.Functions{
 	"array_length": sql.Function1(NewArrayLength),
 	"split":        sql.Function2(NewSplit),
 	"concat":       sql.FunctionN(NewConcat),
-	"lower": 		    sql.Function1(NewLower),
-	"upper": 		    sql.Function1(NewUpper),
+	"lower":        sql.Function1(NewLower),
+	"upper":        sql.Function1(NewUpper),
 	"ceiling":      sql.Function1(NewCeil),
 	"ceil":         sql.Function1(NewCeil),
 	"floor":        sql.Function1(NewFloor),
 	"round":        sql.FunctionN(NewRound),
+	"coalesce":     sql.FunctionN(NewCoalesce),
 }