JPH02273868A - Character-string data retrieving system - Google Patents

Abstract

PURPOSE:To shorten the retrieval time by calculating an integer value based on a value of character-string data, executing a large/small comparison of the integer value and executing a character-string comparison of the character- string data only in the case a result of comparison is equal. CONSTITUTION:Based on a value of first character-string data designated from a user, a first integer value is calculated by using an integer value generating means 3 and second character-string data stored in a data base 5 and first character-string data are compared. In this case, a large/small comparison of a second integer value stored in the data base together with second character- string data and a first integer value is executed, and only in the case its result is equal, a character-string comparison of first character-string data and second character-string data is executed, and in other case, a result of comparison of each integer value is set as a result of comparison of the character-string data. In such a way, the total number of comparison required for retrieving the character-string data is curtailed, and the retrieval time is shortened.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention searches a database and extracts predetermined character string data from the database in response to a user's request to search for character string data in a database. Concerning string data search methods.

[Conventional technology]

As a string search method, in response to a search request from a user consisting of a condition for comparing the size of string data to a database, first string data specified by the user and second string data stored in the database are sent to the database. A known method is to perform a size comparison with character string data and extract from a database character string data whose result satisfies the size comparison condition specified in the search request. Conventionally, in this type of string search method, only string data is stored in a database as string data information, and the first string data and second string data are one character from the beginning of one string data. The size comparison was performed one by one, and the result of the size comparison at the first point where they were not equal was used as the result of the size comparison of the string data, and if all characters were equal, the two string data were determined to be equal. .

[Problem to be solved by the invention]

However, in the conventional character string search method described above, when comparing the first character string data specified by the user with the second character string data stored in the database, the characters are compared character by character from the beginning. Therefore, as the size of the character string data increases, the number of times that comparisons are performed for each character increases, resulting in a longer search time. In particular, when much of the character string data stored in the database starts with the same character, there is a drawback that the number of comparisons required to search for the character string data becomes large.

The present invention has been made to improve these conventional drawbacks, and its purpose is to provide a string data search method that can reduce the total number of comparisons required for string data searches and shorten the search time. It is in.

[Means to solve the problem]

The character string data search method of the present invention has an integer value generation means for calculating an integer value whose size can be compared based on the value of character string data. Both the value itself and the integer value calculated by the integer value generation means are stored in the database. In response to a search request from a user that includes a size comparison of character string data, a first value is generated using the above-mentioned integer value generation means based on the value of the first character string data specified by the user. Calculate an integer value and combine the second string data stored in the database and the first
When comparing the string data of Only then, a character string comparison is performed between the first character string data and the second character string data, and in other cases, the comparison result between the integer values is used as the comparison result of the character string data. An integer value generated based on certain character string data is greater than or equal to an integer value generated based on character string data that is υ smaller than that character string data. Similarly, an integer value generated based on certain character string data is smaller than or equal to an integer value generated based on character string data larger than that character string data. Therefore, except when the comparison results of integer values are equal, the comparison result of integer values becomes the comparison result of character string data.

[Effect]

In this method, by performing a size comparison between integer values generated based on string data in advance, most of the string data that has no possibility of satisfying the size comparison condition specified in the search request is removed. Can be excluded from candidates. Compared to the conventional method, the number of comparisons between integer values will increase once, but as a result, many comparisons of character string data that require character-by-character comparisons can be omitted. As a result, it is expected that the total number of comparisons required for character string data search will be reduced and the search time will be shortened. [Example] Next, an example of the character string data search method of the present invention will be explained using drawings. This will be explained in detail.

Referring to FIG. 1, one embodiment of the present invention includes an input means 1
, character string data storage means 2, and integer value generation means 3 and 1
It is composed of a character string data comparison means 4, a database 5, and an output means 6.

The user specifies a search request consisting of storage of character string data or size comparison conditions through the input means 1, and
Then, enter the value of the required string data. Further, the search results are outputted through the output means 6.

Tel! 1 database 5 is similar to that used in normal database management systems. The character string data storage means 2 stores the character string data input from the input means 1, the integer value generation means 3 generates an integer value from the character string data, and the character string data comparison means 4 stores the character string data input from the input means 1. The character string data thus obtained is compared with the character string data in the database 5.

Next, a processing example of such a character string data search method will be explained using FIGS. 2 to 7.

FIG. 2 is a flowchart showing the flow of processing in the character string data storage means 2. Referring to FIG. 2, the one-character string data storage means 2 first receives an input of character string data to be stored from the user via the input means 1 (step 21). Next, specify this character string data and call the integer value generation means 3 to generate an integer value (Stella f2
2).

Finally, the integer value generated by the integer value generation means 3 is stored in the database 5 together with the value of the character string data input by the user (step 23).

FIG. 3 shows the structure of integer values generated by the integer value generation means 3. Referring to FIG. 3, the 1-bit integer value generated by the integer value generation means 3 is composed of groups corresponding to the first n characters of the character string data. All characters that can be stored as character string data are 2 class 11” to class 1 m # m in character code order.
The characters are divided into classes, and each group that constitutes an integer value is set with a value indicating the class code of the corresponding character. If the character string data is shorter than n characters, O will be added later as an empty class code. Letting α be the number of pits required to represent m class codes and an empty class code, the following formula holds true.

α "f1 day" k ≧ nx α Here, rxl represents the largest integer that is equal to or smaller than X.

FIG. 4 shows an example of integer values generated by the integer value generation means 3. Referring to Figure 4, the integer value is 3
The first W4B character of the character string data is divided into 15 classes. In reality, when determining the number of groups and classes and the method of dividing characters into m classes, consideration is given to the distribution of characters that can be included in one character string data, the regularity of character string data stored in the database, etc. You can decide which one is best for each system.

In Figure 5 (1) and (b), the character string 'Data bas
e', an integer value of 2 generated based on '5yst@m'
An example of a hexagonal image is shown for each.

FIG. 6 is a flowchart showing the flow of processing in the integer value generation means 3. Referring to FIG. 6, the integer value generation means 3 first sets a variable X for storing an integer value to 1.
Initialize the variable C to 0# (step 501), initialize the variable C for storing the character to be processed next to the first character of the string data (step 502), change the string of stored characters to 99 e K. Initialize variable 1 for storing the position in the data to 11" (step 503). Next, assign the class code of the character stored in variable C to variable y (step 504), and set the current variable As a result of shifting the value of y to the upper direction by the value of the number of bits α necessary to express m class codes and empty 2 code, y
Assign the sum of the values of as the new value of variable X (
Step 505).

Note that in the Stella f505, the symbol "ku" indicates a shift operation. Next, the value of the variable l is compared with n, which is the number of groups (step 506), and if they are equal, the process ends. 1
If and n are not equal, determine whether the character stored in C is the last character of the string data.
7), If C is not the last character, assign the next character in the string data to %C (Stella f508), assign the value obtained by adding 1 to the current value of t to 1 (Stella f509), Stella The process returns to f504 and continues processing. If C is not the last character, substitute 10'' for y (step 510).
, returns to Stella f505 and continues processing.

FIG. 7 is a flowchart showing the flow of processing in the character string data comparison means 4. Referring to FIG. 7, the character string data comparison means 4 first inputs the first
Receives input of character string data from the user (step 601), specifies this character string data, calls the integer value generation means 3, and generates a first integer value (step 60).
2). Next, the second character string data stored in the database 5 is read (Stella 7'603), and it is determined whether the character string data exists (step 604).
If the character string data does not exist, the process ends; if the character string data does exist, the second integer value stored together with the second character string data is read (step 605). Next, the first
Compare the integer value with the second integer value (Stella 7
”606), it is determined whether the comparison results are equal or not (step 607). If the comparison results are equal, the first character string data and the second character string data are divided one character at a time as in the conventional method. (Step 609), and determines whether the character string data included in the search request satisfies the size comparison condition (Step 610). Stellar 7'611) then returns to Stellar 7'603 to output the second character string data.If the condition is not satisfied in step 610, the process returns to Stellar f603 and repeats the process without outputting the character string data. Also, in step 607, the first
If the magnitude comparison result between the integer value and the second integer value is not equal, it is determined whether the magnitude comparison result matches the magnitude comparison condition of the character string data included in the search request (Step 608), When the second
Then, the process returns to step 603. If there is a match in step 608, the process returns to step 603 and repeats the process without outputting the character string data.

〔Effect of the invention〕

As explained above, in the string data search method of the present invention, many strings that are unlikely to satisfy the search request can be excluded from candidates without actually comparing the string data character by character. Therefore, it is expected that the total number of comparisons required for character string data searches will be reduced and the search time will be shortened. This is particularly useful if most of the string data stored in the database starts with the same value.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the character string data search method of the present invention, FIG. 2 is a flowchart showing the processing flow of the character string data storage means 2, and FIG. FIG. 4 is a diagram showing an example of an integer value generated by the integer value generation means 3, and FIGS. 5(a) and (b) are specific examples of the generated integer value. FIG. 6 is a flowchart showing the processing flow of the integer value generation means 3, and FIG. 817 is a diagram showing the processing flow of the character string data comparison means 4. In FIG. 1, 1... input means, 2... character string data storage means, 3
. . . integer value generation means, 4 . . . character string data comparison means, 5 . . . database, 6 . . . output means. Figure 3 Wk4 Figure

Claims (1)

[Claims] An integer value generation means for calculating an integer value whose size can be compared based on the value of character string data, and a character specified by a user in response to a request from the user to store character string data in a database. a string data storage means for storing the column data in a database together with the integer value calculated by the integer value generation means; and a string data storage means for storing the column data in the database together with the integer value calculated by the integer value generation means; A first integer value is calculated using the above-mentioned integer value generation means based on the value of the first character string data specified by the user, and the first character string data specified by the user and the second character in the database are calculated. When comparing column data based on a search request, the second integer value stored in the database together with the second character string data is compared with the first integer value, and if the comparison results are equal, String data comparison means that performs a string comparison between the first string data and the second string data, and if the comparison results are not equal, the comparison result of the integer values is used as the comparison result of the string data. A character string data search method comprising: