This example of filter hook is in which to narrow down the data by a plurality of conditions to the values stored in one column. This code should be inserted to as like "functions.php" in your theme.

narrow-down-one-column.php

<?php
// In the variables of "$target_tables", "$narrow_column", "$narrow_keywords", you should be optimized by your environment and project.

function custom_filter_sql( $sql, $table_name, $sql_clauses ) {
  $target_tables = [ 'your_table_name' ];
  $narrow_column = 'specific_column_name';
  $narrow_keywords = [ 'keyword1', 'keyword2', 'keyword3' ];
  if ( in_array( $table_name, $target_tables ) ) {
    if ( is_array( $sql_clauses[1] ) ) {
      // Narrowing is find_data()
      $_add_query = "AND `". $narrow_column ."` IN ('". implode( "','", $narrow_keywords ) ."')";
      foreach ( $sql_clauses[1] as $_i => $_union_query ) {
        $_before_query = function_exists( 'mb_substr' ) ? mb_substr( $_union_query, 0, -1 ) : substr( $_union_query, 0, -1 );
        $sql_clauses[1][$_i] = $_before_query . $_add_query . ')';
      }
      $sql = implode( ' ', $sql_clauses[1] ) .' '. $sql_clauses[2] .' '. $sql_clauses[3];
    } else {
      // Narrowing is get_data()
      $_new_sql = <<<SQL
SELECT %s 
FROM %s
%s
%s %s
SQL;
      $_add_query = "`". $narrow_column ."` IN ('". implode( "','", $narrow_keywords ) ."')";
      $_where_clause = empty( $sql_clauses[1] ) ? 'WHERE '. $_add_query : $sql_clauses[1] .'AND '. $_add_query;
      $sql = sprintf( $_new_sql, $sql_clauses[0], $table_name, $_where_clause, $sql_clauses[2], $sql_clauses[3] );
    }
  }
  return $sql;
}
add_filter( 'cdbt_crud_find_data_sql', 'custom_filter_sql', 10, 3 );
add_filter( 'cdbt_crud_get_data_sql', 'custom_filter_sql', 10, 3 );