[GitHub] [calcite] pengzhiwei2018 commented on a change in pull request #1168: [CALCITE-3005] Implement string functions: LEFT, RIGHT

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pengzhiwei2018 commented on a change in pull request #1168: [CALCITE-3005] Implement string functions: LEFT, RIGHT
URL: https://github.com/apache/calcite/pull/1168#discussion_r276142271
 
 

 ##########
 File path: core/src/main/java/org/apache/calcite/runtime/SqlFunctions.java
 ##########
 @@ -243,6 +243,26 @@ public static int ascii(String s) {
         ? 0 : s.codePointAt(0);
   }
 
+  /** SQL LEFT(string, int) function. */
+  public static String left(String s, int n) {
+    if (n < 0) {
+      return "";
+    } else {
+      int len = s.length();
 
 Review comment:
   It is better to add a null-test for `s`.

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