Merge pull request #159 from kblomster/mysql-comparison-functions

mysql: export some conditional functions

mysql/functions.go

@@ -261,10 +261,22 @@ func UNIX_TIMESTAMP(str StringExpression) TimestampExpression {
 	return jet.NewTimestampFunc("UNIX_TIMESTAMP", str)
 }
 
-//----------- Comparison operators ---------------//
+// --------------- Conditional Expressions Functions -------------//
 
 // EXISTS checks for existence of the rows in subQuery
 var EXISTS = jet.EXISTS
 
 // CASE create CASE operator with optional list of expressions
 var CASE = jet.CASE
+
+// COALESCE function returns the first of its arguments that is not null.
+var COALESCE = jet.COALESCE
+
+// NULLIF function returns a null value if value1 equals value2; otherwise it returns value1.
+var NULLIF = jet.NULLIF
+
+// GREATEST selects the largest value from a list of expressions, or null if any of the expressions is null.
+var GREATEST = jet.GREATEST
+
+// LEAST selects the smallest value from a list of expressions, or null if any of the expressions is null.
+var LEAST = jet.LEAST