Parent topic: Using query by example
Query by example (CONSTRUCT) / Using query by example

Query operators in CONSTRUCT

The CONSTRUCT instruction supports a specific query syntax, using wildcard characters and comparison operators.

The table below lists CONSTRUCT wildcard characters that can be used during a query by example input:

Table 1. CONSTRUCT relational operators
Symbol Meaning Data type
value Use value as is to filter Any simple type
= (without value) Is NULL Any simple type
== value Equal to value Any simple type
> value Greater than value Any simple type
>= value Greater than or equal to value Any simple type
< value Less than value Any simple type
<= value Less than or equal to value Any simple type
<>value or !=value Not equal to value Any simple type
<> or != (without value) Is not NULL Any simple type
value1:value2.. Range from value1 to value2 Any simple type
value1|value2 [...] List of values Any simple type
* Wildcard for any string Char string types
? Single-character wildcard Char string types
[c1-c2] Range of characters Char string types
[c1c2 [...] ] Set of characters Char string types

Queries based on character types are case sensitive, because SQL is case sensitive, except if the database server is configured to be case-insensitive.

The * (star) and ? (question mark) wildcards are specific to character string type queries, and will generate a MATCHES expression or a LIKE expression, depending on the type of database used. When entering a * or ?, the pattern can also contain a character range specification with the square brackets notation [a-z] or [xyz]. A caret ( ^. ) as the first character within the square brackets specifies the logical complement of the set, and matches any character that is not listed. For example, the search value [^AB]* specifies all strings beginning with characters other than A or B.

Some syntaxes can produce an "Error in field" dialog error if the feature is supported by the pattern matching operator of the database server. For example, not all db servers support the [a-z] character range specification in the LIKE pattern.

If you want to search for rows with values containing a * star, a ? question mark or a \ backslash, you must escape the wildcard character with a backslash. Specifying a backslash before another character will have no effect.

Table 2. CONSTRUCT input examples with matching and non matching values
QBE input example Matching values Non matching values
100 100 99, 101, NULL
>=100 100, 101, 200 10, 99, NULL
!=100 98, 98, 101, 102 100, NULL
!= 98, 99, 100, 101 NULL
1:100 1, 2 ... 99, 100 0, 101, NULL
aaa:yyy aaa, aab, ab, yy, yyy zaa, NULL
abc abc bc, abcd, Abc, NULL
ABC ABC abc, aBC, NULL
abc* abc, abcd, abcdef bc, ABC, NULL
*bc abc, bc acd, aBC, NULL
?bc abc, xbc, zbc aabc, aBC, NULL
*bc? aaaabc, abcd, bcd abcdef, bcdef, NULL
[a-z]bc abc, ebc, zbc 2bc, +bc, Abc, NULL
[^abc]* deee, feee, zyx, z azzz, byy, d, NULL
a[bxy]c abc, axc, ayc a2c, azc, aBc, NULL
*[xyz] abcx, eeeez abcd, eeee, NULL
1|2|35 1, 2, 35 4, 5, 6, NULL
aa|bb|cc aa, bb, cc ab, dd, NULL
\\abc* \abc, \abcdef abc, NULL
\*bc *bc abc, bc, NULL
*\[?\]* [a], a[b]c, xx[y]zz a[bb]c, a[]c, NULL
Parent topic: Using query by example