Abstract: A set of sorted columns of one table stored in a DB machine are binary-searched by a hardware in synchronism with data transfer when another table is read from a disk unit, to select a row to be joined. Where a key word sequence to be searched is stored in ascending or descending order, determination of a maximum address in an area in which key words smaller than a search key are stored and determination of a maximum address in an area in which the key words smaller than or equal to the search key are stored are parallelly executed to determine the store range in one searching.

Abstract: A skip table is prepared from which a state of a subsequent symbol string and an address of one or plural symbols to be subsequently inputted can be readily determined by making reference to a set of a current symbol string search state and one or plural symbols to be subsequently inputted of the symbol string. When executing searching for the symbol string, data stored in the skip table are looked up to assure the symbol string search by inputting only a minimized number of necessary characters of the symbol string. Necessity of inputting all the characters of the symbol string for searching is eliminated and the processing speed can be increased considerably. A plurality of symbol strings may be searched for.

Abstract: Disclosed is a method for controlling a rotary memory device for recording information on a recording medium in the form of a track, in which method the respective areas, such as a count section, a key section and a data section, which constitute a record format in the form of a record, are stored in the respective sectors each having a fixed length.