The function wizard tells, that the second parameter (Database field) is required, but it is optional, see 70806. And with ODF 1.3 this is standard. The text in the function wizard needs to be adapted. The help is already correct.
repro, Version: 7.0.0.0.alpha1+ (x64) Build ID: b587de60d4e6aa96238766272d94f1499b22f696 CPU threads: 8; OS: Windows 6.1 Service Pack 1 Build 7601; UI render: default; VCL: win; Locale: de-DE (de_DE); UI: en-US Calc: took some time to spot it, have a cell with DCOUNT[A] formula, set focus on it, click formula wizard right to 'name box', click into the formula shown in the box 'Formula' bottom right of the wizard dialog, place cursor on the second parameter, comment above says 'Database field (required)', is like that at already in ver. 4.1.6.2, inherited? i could add that the function doesn't count the 'cells' in the range but the rows or datasets? and that 'Indicates which database field (column) is to be used for the search criteria' is also questionable, on a first view the search criteria is applied by matching the headers of the 'Database' and 'search criteria' definition, while the 'Database field' parameter - if given - restricts the result to rows (datasets) in which the column it indicates evaluates to a numerical value,
Winfried Donkers committed a patch related to this issue. It has been pushed to "master": https://git.libreoffice.org/core/commit/885465bc0ae6029d8adad57015fb0ff6c26a6ba6 tdf#133353, Make 2nd argument optional for DCOUNT and DCOUNTA. It will be available in 7.4.0. The patch should be included in the daily builds available at https://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: https://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.
Winfried Donkers committed a patch related to this issue. It has been pushed to "libreoffice-7-3": https://git.libreoffice.org/core/commit/1db4d3c869dbd4d68c0ab7b15c60bb2dad0a9f67 tdf#133353, Make 2nd argument optional for DCOUNT and DCOUNTA. It will be available in 7.3.0.0.beta2. The patch should be included in the daily builds available at https://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: https://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.