postgresql instr函数功能实现(实现oracle plsql instr相同功能)

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### Code Reference

• DESC:postgresql instr函数功能实现(实现oracle plsql instr相同功能)
• Last Update:2020-6-24 17:58
  • postgresql instr函数功能实现(实现oracle plsql instr相同功能)
    • Snippet:
      
      Jupyter Code

      -- 实现1
      CREATE FUNCTION instr(varchar, varchar) RETURNS integer AS
        $$ DECLARE pos integer;
      BEGIN
        pos := instr($1, $2, 1);
        RETURN pos;
      END;
      $$ LANGUAGE plpgsql STRICT IMMUTABLE;    
      
      -- 实现2                    
      CREATE FUNCTION instr(string           varchar,
                            string_to_search varchar,
                            beg_index        integer) RETURNS integer AS
        $$        DECLARE pos integer NOT NULL DEFAULT 0;
        temp_str  varchar;
        beg       integer;
        length    integer;
        ss_length integer;
      BEGIN
        IF beg_index > 0 THEN
          temp_str := substring(string FROM beg_index);
          pos      := position(string_to_search IN temp_str);
        
          IF pos = 0 THEN
            RETURN 0;
          ELSE
            RETURN pos + beg_index - 1;
          END IF;
        ELSIF beg_index < 0 THEN
          ss_length := char_length(string_to_search);
          length    := char_length(string);
          beg       := length + beg_index - ss_length + 2;
          WHILE beg > 0 LOOP
            temp_str := substring(string FROM beg FOR ss_length);
            pos      := position(string_to_search IN temp_str);
            IF pos > 0 THEN
              RETURN beg;
            END IF;
            beg := beg - 1;
          END LOOP;
          RETURN 0;
        ELSE
          RETURN 0;
        END IF;
      END;
      $$ LANGUAGE plpgsql STRICT IMMUTABLE;
      
      -- 实现3
      CREATE FUNCTION instr(string           varchar,
                            string_to_search varchar,
                            beg_index        integer,
                            occur_index      integer) RETURNS integer AS
        $$           DECLARE pos integer NOT NULL DEFAULT 0;
        occur_number integer NOT NULL DEFAULT 0;
        temp_str     varchar;
        beg          integer;
        i            integer;
        length       integer;
        ss_length    integer;
      BEGIN
        IF beg_index > 0 THEN
          beg      := beg_index;
          temp_str := substring(string FROM beg_index);
          FOR i IN 1 .. occur_index LOOP
            pos := position(string_to_search IN temp_str);
            IF i = 1 THEN
              beg := beg + pos - 1;
            ELSE
              beg := beg + pos;
            END IF;
            temp_str := substring(string FROM beg + 1);
          END LOOP;
        
          IF pos = 0 THEN
            RETURN 0;
          ELSE
            RETURN beg;
          END IF;
        ELSIF beg_index < 0 THEN
          ss_length := char_length(string_to_search);
          length    := char_length(string);
          beg       := length + beg_index - ss_length + 2;
          WHILE beg > 0 LOOP
            temp_str := substring(string FROM beg FOR ss_length);
            pos      := position(string_to_search IN temp_str);
            IF pos > 0 THEN
              occur_number := occur_number + 1;
              IF occur_number = occur_index THEN
                RETURN beg;
              END IF;
            END IF;
            beg := beg - 1;
          END LOOP;
          RETURN 0;
        ELSE
          RETURN 0;
        END IF;
      END;
      $$ LANGUAGE plpgsql STRICT IMMUTABLE;