code: function selectById () {
      // always select all columns
      _.each(this.model.columnNames, columnName => {
          // get column spec
          var spec = this.model.columns[columnName]
          // add select column sql
          this.select.push(
              this.selectColumnSql(this.model, columnName, spec, this.table)
          )
      })
      // build query parts
      this.selectSql = `SELECT ${this.select.join(', ')}`
      this.fromSql = `FROM ${this.quoteName(this.table)} ${this.alias}`
      this.whereSql = this.selectByIdWhereSql()
      // build full query
      this.sql = `${this.selectSql} ${this.fromSql} ${this.whereSql}`
  }
docs: @function selectById
  
  build select by id query
  
  @throws {Error}